What do these two places have in common? On the right, below, is Stonehenge, the iconic monument in England, dating from roughly 3000 BC; on the left is the Basilica of San Vitale, in Ravenna, Italy, first built in 526, on the orders of Bishop Ecclesius of Ravenna, after the capital of the Roman Empire was transferred from Milan to Ravenna, in 402 AD. They are both built on an octagon and inner circle plan. Are these similarities worthy of investigation? If so, what might the octagon and circle design reveal, and how widespread is it in the history of architecture?

Below is the ground plan of the Basilica in Ravenna, an octagon and circle, within an octagon. (note: the north pointing arrow on the diagram below is incorrect, which can be verified on Google Earth)

This is the plan of Stonehenge from the English Heritage archive:

And below is a ground plan of Stonehenge, showing the Aubrey Circle highlighted in yellow, and the line of sight to the first point of the summer solstice sunrise in yellow. In green, the rectangle corresponds to the four Station Stones, on the Aubrey Circle. This rectangle is compatible with being part of an octagon within the Aubrey circle, that is, the shorter sides of the rectangle are the right length to fit eight times joined up together inside the yellow circle.

At Stonehenge the octagon is not quite as clear-cut as at Ravenna. The main structure at Stonehenge, working from the centre outwards, is a central U-shaped pattern of bluestones, then another U-shaped pattern of sarsen trilithons, surrounded by a circle of bluestones, and an outer circle of sarsen stones, then a circle of bluestones, then a circle of sarsen stones, then a circle of 'Y' stones, then a circle of 'Z' stones, then a circle of post holes named after their discoverer, Aubrey, and finally a large circular earthwork. The problem is that if the four Station Stones which make up the large rectangle in green form two 5-12-13 Pythagorean triangles, then the angles aren't quite right for this rectangle to also form the centre part of a great octagon. This was pointed out by Jim Alison on the GHMB website. A 5-12-13 triangle has angles of 90°, 67.38° and 22.62°. A similar triangle within an octagon would have dimensions of 5, 12.07 and 13.066, with angles of 90.017°, 67.484°, and 22.499°. Some researchers are inclined to think that as there is clearly a 5-12-13 triangle at work, the octagon option is not part of the intended design. However, others believe that due to the size of the Station Stones, both the Pythagorean triangle and the octagon are possible. It's a matter of interpretation.

I happened to see the floor plan of the Ravenna Basilica, while browsing online, and it struck me that the circle and octagon structure of the plan was very similar to the plan of Stonehenge. Inspired by David Genevier's recent work, comparing the plans of two apparently very different structures, I decided to superimpose the two images to see if the proportions had anything in common. To get the best match I swiveled the Basilica image around, so this does not show the correct orientation. I found that the similarity was striking. An inner circular structure, and outer octagonal structure, and an axis pointing north-east in Stonehenge's case, and south-east in the Basilica's case.

Below, the Ravenna Basilica plan has been swiveled round to the correct orientation (according to my measurement on Google Earth), and shows lines corresponding to various sunrise azimuths: the solstices, the winter Phi day (when night and day are in Phi ratio), and the main axis of the structure, which cannot correspond to a solar event as it is beyond the possible azimuths for any sunrise at Ravenna.

At first glance, there seem to be very strong similarities in the proportion and design of Stonehenge and the Basilica di San Vitale of Ravenna. An octagon, an inner circle, or several, and a protrusion through the circle and octagon, in Stonehenge's case, directed at an important solar event, the summer solstice sunrise.

A closer look at Stonehenge

Below is a diagram comparing the angles between the Station Stones as described by Hawkins, against the values you would expect in the rectangle had perfect 90 degree angles. As we saw above, if the Station Stones are taken to make up a perfect rectangle, with 90 degree angles, then the angles produced by the diagonal will be 67.38° and 22.62°, and if we are dealing with an octagon we can expect to find angles of 90.017°, 67.484°, and 22.499°. The numbers in blue correspond to Hawkins's figures, and while two of the 'right angles' are just over 90 degrees (stones 91 and 92), the other two (stones 93 and 94) are just under. So already there is a certain degree of ambiguity. I've written in below, in black, the ideal figures for the 5-12-13 triangle, but not for the octagon, to keep it easy to read. The Pythagorean triangle is just as likely an explanation as the octagon, in my view, both being compatible with the angles recorded by Hawkins, within a fairly small margin of error.

The table below shows a summary of measures at Stonehenge, courtesy of Euan MacKie, and the diagram underneath shows some of these measures. The measures are loosely compatible with both a Pythagorean triangle and an octagon. For example, taking 33.23 m as a short side, divided by 5 and multiplied by 13 gives 86.398 m (for a Pythagorean triangle). And the same divided by 5 multiplied by 13.066 gives 86.836636 (for an octagon). Both compare reasonably well to 86.66 m and 86.44 m, given int the table, for the distance bewteen stones 93 and 91, and 92 and 94. the number is eight is present in the long side of the rectangle, as it is close to 80 metres long. (If the metre at Stonehenge seems anachronistic, it is a metre of 54 Roman or Egyptian digits, or three Northern or Saxon feet.)

Below are two nice consequences of a potential octagon at Stonehenge. The first is that the total area of two overlapping squares fitting within the Aubrey circle arranged around a central point of symmetry, so that the distance between each corner is 1,3125 inches, is 12,960,000 square digits of 0.729166667 inches.

Another is that if the side of the octogon is 33.3333 metres (based on a slight re-interpretation of MacKie's table), then the perimeter would be 800/3 metres. One octogon side is then 800/24 metres, or 100 Northern or Saxon feet of 13.125 inches, giving a perimeter of 800 Northern or Saxon feet. I was lucky enough to be able to work on this with Jim Alison a year or so ago.

The star of Ishtar has eight points and a circle in the middle, and is compatible with the plan of Stonehenge. Ishtar, or Inanna is associated with Venus. But is the octagon, if it is at Stonehenge, or at Ravenna, linked to Venus in any way? Or is the octagon simply to be understood as two squares, the square being a perfect and highly symbolic shape, with no reference to the moon or Venus?

Leaving the octagon theory aside for now, the Pythagorean triangles formed by the Station Stones are in themselves very interesting. One possible consquence of a 5-12-13 triangle between the Station Stones is that the hypotenuse, drawn in dark blue below, provides the direction for the side of a 1:1:√2 triangle, or half a square, with sides of 20 metres, as per the diagram. The hypotenuse of this little triangle points to the Heel Stone (green line). Building from that triangle a spiral of Theodorus, the last hypotenuse beore the spiral begins to overlap onto itself is √17, and this is the turquoise blue line below, bissecting the short side of the Statio Stone rectangle at the 3/5 point. To check this, we can take the long side of the Station Stone rectangle as 80 metres, the short side as 33.333 metres, and divide by long side by 80/4 = 20, and multiply by √17, obtaining 82.4621 metres. A right angle triangle with one side of 80 metres and another of 82.4621 metres will have a third side of 20 metres, which is 33.3333 x 3/5. In this way, a spiral of Theodorus fits in with the Station Stone rectangle and Heel Stone, if the dimensions of the rectangle are given as 33.3333 x 80 metres. Perhaps this geometry can also be found at Ravenna.

A closer look at Ravenna

Below are two Google Earth shots of the Basilica of Ravenna, the first shiowing the azimuths for the solstice sunrises, and the second the orientation of the protrusion, which is beyond the scope of the sun's movements, so is presumably stellar. Unfortunately I don't have any measures for the Ravenna Basilica, or most of the other places mentioned there.

There are other octagonal buildings in Ravenna, a mausoleum and two baptistries. Curiously, one of the measures in the image below is 8 metres.

The Battistero degli Ariani was built by King Theodoric at the end of the fifth century, when Arianism was the official religion of the court.

The other is the Battistero Neoniano (o degli Ortodossi). It's most ancient monument in the city, being late 4th century, and was partly erected on the site of a Roman Bath. The baptistry was part of a great Basilica, which was destroyed in the 18th century. Inside, the building is completely covered in mosaics, many with animal and plant motifs, such as vines, spirals of acanthus, and peacocks, all symbols of eternal life. Inside the magnificent dome is a mosaic depicting St John the Baptist pouring water over Jesus who is standing in the river Jordan, together with another figure said to be Zeus, personifying the river. On the central circle of this mosaic are sixteen divisions, with golden branches emanating from each one. This seems to reinforce the idea of light pouring in at an angle corresponding to a division of a circle into sixteen parts.

David Warner Mathisen has done extensive research into the stellar associations of mythical figures, and it seems that the figure of Jesus standing in the river Jordan is associated with Ophiuchus, a major constellation, with one foot in the Milky Way. The figure of St John the Baptist, with his bent leg, seems to correspond to Hercules, the constellation situated directly above Ophiuchus in the sky. Alternatively, he could correspond to Orion, a constellation directly across the sky from Ophiuchus, who is often depicted with a bent left leg, and outstretched arms. The river Jordan itself becomes associated with the Milky Way. Baptism signifies rebirth in the Christian religions, and it is curious that the point in the sky where souls headed after the death of the body in the ancient Egyptian religion was the Golden Gate, located at the point where Ophiuchus's foot meets the Milky Way. This is technically referred to as part of Sagittarius now, and also corresponds to the centre of the galaxy. Many divine figures can be linked to the two constellations Ophiuchus and Hercules, as David Warner Mathisen has demonstrated.

The image below shows the relative positions of Ophiuchus, Sagittarius A*, and the Milky way.

And below is an image from H.A. Rey's book The Stars, illustrating the constellation Ophiuchus, with Hercules above it.

What can be proposed at this point is that the numbers eight and sixteen are connected, in the ceiling at the Ravenna Baptistry, to rebirth, and that this association goes back to the earliest Christian times, and possibly to pre-Christian times. In the same way that the part of the sky associated with death and rebirth to the Ancient Egyptians may also be referred to in this Early Christian art at Ravenna .

The mosaic suggests the importance of water, both through the imagery of the River Jordan, which itself perhaps symbolises the Milky Way, and the ritual of baptism. The fact that the site was once a Roman bath, and may be located on or near a spring, confirms the importance of water.

There is a fifth century baptistry in Naples, with a similar geometric design, though the room itself is square, not octagonal, and encloses a circle (a baptismal plunge pool). However, the ceiling is octagonal. It is considered the oldest paleo-Christian baptistry in the west.

This is a similar design to the two buildings in Ravenna.

Aachen

Another place built at the site of Roman baths, famed for its thermal waters, and whose church was definitely inspired by Ravenna, is at Aachen, once Charlemagne's capital. Below are two images showing the ground plan of Charlemagne's chapel at Aix-la-Chapelle, as it was known then, the name being derived from the Latin for water acquis: an octagonal domed hall surrounded by aisles, and on the outside, a regular polygon of sixteen sides.

Ravenna was the capital of the Western Roman Empire for a short time, from the start of the fifth century, and Aix-la-Chapelle was the capital of Frankish Empire from the tenth century. From then until the turn of the nineteenth century all the emperors of the Holy Roman Empire, the most powerful monarchy in Europe, were crowned there. All three places, Ravenna, Aix-la-Chapelle (Aachen) and Stonehenge were all important centres.

The protrusion from the circle and octagon at Aix-la-Chapelle points due east. So presumably, it is oriented to the equinox sunrise. That's hardly specific to any particular latitude: the equinox always corresponds to an easterly sunrise.

The number 8

In astronomy, there are two periods of time that last roughly eight years, one is to do with the Moon, the other is with Venus, two heavenly bodies associated with the goddess Venus / Ishtar / Inanna.

A Great Year of 100 lunations is almost exactly eight years. The figure is in fact 29.53059 x 100 /365.242199 = 8.08521, or eight years and a month of 31.09 days. Ten Great Years, or 1000 lunations, multiplied by pi and divided by the number of days in a year gives 254.0042877. This is close to the number of metres corresponding to 10000 inches. 8 is a Fibonacci number, and 8.08521 /5 = 1.617042, close to Phi.

Perhaps the most important association with the number eight, in terms of measuring time, is Venus. From Earth, Venus moves in a pattern that repeats every eight years, that is, Earth orbits the sun eight times for every thirteen orbits of Venus. This is known as the eight-year cycle of Venus, because 13 Venusian orbits (8 x 224.701 days) are very nearly equal to eight Earth years. Venus's path describes a pentagram, as seen from our planet. Earth's relationship to Venus, thus involves three Fibonacci numbers, 5, 8 and 13. The Pythagoreans related the number eight to the goddess Venus.

Eight is an important number in myth and religion. In Old Kingdom Egyptian mythology, the Ogdoad (Greek - "the eightfold") were eight primordial deities, who were worshipped in Hermopolis Magna. The Ogdoad is an ancient Egyptian cosmological concept that assigned four pairs of deities to infinite time, darkness, the primeval waters, and the void to pre-creation. that embodied the four components of pre-creation (). As we mentioned earlier, the Egyptian creation myth developed in late and Ptolemaic times was based heavily on that of Hermopolis, references to the Ogdoad appearing in texts as early as the 25th Dynasty. Before the Greeks, Hermopolis was named Khmunu (‘Eight Town’ or ‘City of the Eight’), and the Coptic name ‘shmun’ also means eight, associated with the god Thoth, the counterpart of Hermes. But it is to with the moon that Thoth and Hermes are associated, not to Venus. There are the remains of a fifth century basilica there, and I had a look for any octagons, but there were none. (See here)

According to Wallis Budge, "Thoth was regarded as a god who was self-begotten and self-produced, that he was One, that he made the calculations concerning the establishing of the heavens, and the stars, and the earth, that he was the heart of Rā, that he was the master of law both in its physical and moral conceptions, and that he had the knowledge of “divine

speech.” " (2). Budge adds that, when depicted as an ape, Thoth is "the god of “equilibrium,” and he appears to be a symbol of the equinoxes. The ape āān is also connected with the moon, for he is often seen with the lunar crescent and disk upon his head".(3)

Eight is an important number in many other traditions and religions. In China, for example, eight is associated with prosperity, and the opening ceremony of the Summer Olympics there began on 8/8/08 at 8 seconds and 8 minutes past 8 pm. In ancient Chinese symbol tradition, similarly to the Egyptian mentioned above, there are Eight Immortals who are said to know the secrets of nature. These immortals control all aspects of life and eight tools of power that can give life and destroy evil.

The ancient city of Babylon had eight gates, and the eighth was named the Gate of Ishtar, named after the goddess of love and war, who was associated with Venus. The star of Ishtar has eight points. The Rub-el-Hizb, the Islamic Star, is an important Islamic symbol, is represented as two overlapping squares. The Star of Lakshmi, the Hindu goddess of wealth, is an eight pointed star made up of two squares. Krishna is the eighth avatar of Vishnu and had eight wives. The Jewish religious rite of Brit Milah, commonly known as circumcision, is held on a baby boy’s eighth day of life, and the festival of Hannukah lasts eight days. The Buddha advocated a Noble Eightfold Path to achieve Nirvana. The Archangel Michael, who is perhaps a divine figure in the tradition of Apollo, Mithras, and other solar figures, is also associated with the number eight. There are eight planetary or celestial gates associated with Mithras, as David Ulansey writes:

David Ulansey's understanding of Mithras not just as a solar figure, but as a god who is even more powerful than the sun, gives an idea of a god who presides over the twelve of the zodiac. And just as in the ancient Chinese and Egyptian traditions, it seems that the number eight was important.

In Christianity, this number eight symbolizes salvation and resurrection, but it also has fundamental Theological concepts. Eight is therefore connected to the sun, or at least to our experience of the sun here on earth, which is the seasons.

It makes sense to divide up the year into two sections at least, because of the process of the days gradually lengthening and gradually shortening or the two halves of the year. And so it makes sense to subdivide these periods, either side of the solstices into two more sections, to coincide with the periods at which the days are of equal length to the nights, or to the period at which the sun appears to rise exactly due east and set due west, the equinoxes. And subdividing each of these quarters further gives eight sections. So dividing the year into eight parts defines it in terms of the solstices, the equinoxes (or days of equal length to the nights), and the cross quarter days: 1st February, 1st May, 1st August and 1st November.

This Greek cross is superimposed on a Greek “chi”, the first letter of the Greek word for “Christ.” It forms a cross with eight arms. Since the number eight is said to be symbolic of death, life, rebirth and regeneration, this cross is often used as a baptismal cross.

Other Octagonal Structures

Other octagonal structures include the Hagia Sofia, and the little Hagia Sofia, the Dome of the Rock, Al-Aqsa Mosque, the octagonal church in Antioch, also known as the Golden Church, and several Christian churches with an octagonal structure such as at Ottmarsheim, and Torhout, and the Church of Santa Maria di Angeli in Florence.

Dome of the Rock

Below is the plan of the interior of the Dome of the Rock, in Jerusalem. Again, the inner circle and the octagon, or rather octagons, as there are two.

At Jerusalem, with a sunrise azimuth of 117.31°, the winter solstice is almost exactly the same as the diagonal of the Station Stone Rectangle at Stonehenge. On the 1st May, the sunrise azimuth is 71.76°, which is close to 72°, and so close to 360/5.

Many other buildings were built according to the plan of the Dome of the Rock, including the Church of St Giacomo in Italy, the Mausoleum of Sultan Suleiman the Magnificent in Istanbul, the Rumbach Street Synagogue in Budapest, the New Synagogue in Berlin. There is a tradition that the architecture of the Dome of the Rock was similar to the Temple in Jerusalem. Raphael and Perugio both picked up on this in their paintings of the Marriage of the Virgin.

St Paul's Cathedral, London

St Paul's is not an octagonal building, in the way that Ravenna's Basilica is. However, the octagon and concentric circles that are present at Ravenna and at Stonehenge are also in the design at St Paul's, especially in Wren's first design, and in the floor plan designed by Dickinson.

Below is the floorplan for the paving of St Paul's, which I have swiveled to its correct orientation, according to Google Earth. This also reflects similar geometrical elements.

The concentric circles in the centre, the larger rectangle and the orientation of the design towards similar points to the east are there in both Stonehenge and St Paul's.

The octagon is actually quite a common theme in religious architecture, especially with mausoleums and baptistries, but also churches, mosques and synagogues. The octagon is not always the central feature, as for example at Westminster Abbey, where the Chapter House is octagonal. What is remarkable is how widespread this design is around the world. Below are a few examples of this.

Pagoda of Fogong Temple

Taj Mahal

St Peter's Basilica

In the following two churches, the circle and octagon themes are picked up in the centre of the buildings.

Florence Cathedral

Florence is a potentially interesting site from a Phi day point of view, as the winter Phi day there, which is either the 10th or 11th of January, depending on the year, sees the sun rise at very close to 120 degrees, and set at close to 240 degrees, i.e. in two points of a six-pointed star. For example on 10 Jan 2023, daylight hours are 09:09:12, and 120.29° and 239.79°, and the following day 09:10:38 and 120.07° and 240.02°. In 2024, 09:10:17, and 120.12°239.96°. There are 1440 minutes in a 24 hour period, which divided by Phi, 1.61803, gives 889.97 minutes, which is 14.8328 hours

Poverty Point

This octagon is harder to make out, and perhaps it is not at all an octagon but simply a circle, but I have included it here: The Poverty Point Octagon. This ancient site consists of six enormous, concentric earthen ridges and several large mounds, including one of the largest in North America.

Conclusion

The concentric circles and octagon present at Stonehenge are compatible with a Pythagorean 5-12-13 triangle and an octagon, and these three motifs, inner circles, outer octagon and 5-12-13 triangle or 5x12 rectangle, are present in various combinations in many important structures around the world, in churches, baptistries, mausoelums, synagogues, and mosques, some of which are among the most important in the world. Sometimes the inner circle is framed by a square. The number eight is often highlighted in several different ways within the design. Does the presence of this geometry in places as far apart as China, India, and Europe point to a very ancient history of the octagon and central circle in architecture, going back even further back than the time of Stonehenge? The number eight seems to be bound up with re-birth, resurrection, water, and perhaps the Milky Way too. Perhaps it also refers both to the moon and to Venus.

While researching this, I was putting off what I was supposed to be studying, which was logistic regression and machine learning. I decided one afternoon to go and sit in the reading room in my university and just get stuck in and stop being distracted by octagons. I did this and it was time well spent, until I sat back in my chair, stretched my neck, looked up and, to my amazement, saw an octagon in the ceiling.

It turned out I was sitting in what was actually a war memorial, and the building itself was in the shape of an octagon, which I had never noticed. Tragically, as I read later, the architect's own son had been killed at Gallipoli. Above the entrance, the goddess of victory Nike's name has been carved into the stone. This made me wonder about the sort of victory that was being referred to, was it of the outcome of the war itself, or of a life of the soul after the death of the body?

Nike herself is connected to the godess Athena, who is close in nature to Inanna and Ishtar, as a warrior goddess, connected to creation.

Athena's temple, the Parthenon, in Greece, has eight huge columns to the front, and sixteen to the side, echoing the octagon.

Ishtar may be connected to Easter, which in several aspects is a festival about re-birth, be it of the year, or the resurrection of Jesus. Bede, in his eighth-century work The Reckoning of Time, wrote about Eostre, the Anglo-Saxon goddess of Spring whose name later gave rise to modern the English "Easter,", and this goddess may provide an etymological connection to the goddess Ishtar. Bede wrote that Ēosturmōnaþ (Old English 'Month of Ēostre', was an English month, corresponding to April, which he says "was once called after a goddess of theirs named Ēostre, in whose honour feasts were celebrated in that month". (4) The old English months were purely lunar, and so the calendar had twelve to thirteen months in a year. He says winter began on a full moon. However. Easter is about combining the cycles of the moon and the sun, specifically the lunar calendar in relation to the spring equinox. Reconciling the cycles of the sun and the moon on a yearly basis must have been symbolically very important, though quite different in nature to reconciling these cycles exactly, as with the Metonic cycle of 19 years. For the Babylonians, the new year actually started with the new moon after the spring equinox, the day after the return of the Sumerian goddess Innana/Ishtar from the underworld. Like Jesus, she also was brought back from the dead on the third day. Ishtar's descent into the underworld is an allegory of the cycle of the seasons.

In the end, the number eight as a number symbolising renewal and rebirth may simply allude to the divisions of the year into the quarter and cross quarter days, presided over by a goddess, be she Venus, Ishtar, Inanna, Eostre, or another divine figure. In this way, 8 is the the return of the new cycle of the year, starting in spring, and the return of life. Who knows how far back in time this idea may go back, and whether it was true for the people who designed and used Stonehenge.

Notes

1. David Ulansey, The Eighth Gate: The Mithraic Lion-Headed Figure and the Platonic World-Soul, The Ancient World, Vol. XXXIV, no. 1 (2003), pp. 67-81, http://www.mysterium.com/eighthgate.html

2. See Budge, E. A., The Gods of the Egyptians, Volume 1, Dover Publications, New York. 1969

3. Ibid.

4. Bede, The Reckoning of Time, Bede, The Reckoning of Time - Beda (Venerabilis.), Beda Venerabilis (helgon.), el Venerable Beda (Santo), Bede Venerabilis Staff, Bede, the Venerable, Saint, 673-735 - Google Books

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Budge, E. A., The Gods of the Egyptians, Volume 1, Dover Publications, New York. 1969

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Jon Gibson: Poverty Point Legends & Lore, The History Press, 2021

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