- Built by
- The emperor Zeno
- Period
- c. 473–490
- Plan
- Four basilicas on a central octagon
- Church area
- 5,000 m²
- Diameter
- 27 m
- Roofing
- A great timber dome, lost in the earthquakes of 526–528
The problem the architects were handed was unusual: build a church around an object that cannot be moved, and let very large numbers of people see it.
Their answer was the octagon. An eight-sided court was raised over the column, and four basilicas were set against it in the shape of a cross — east, west, north and south — so that each opened onto the same central space. Instead of one congregation facing one altar, four halls of people faced inward at a single point. It is one of the most intelligent pieces of planning in late antique architecture, and it exists because of a man who refused to come down.
It was roofed with a great timber dome, carried on the worked stone and its projecting supports. The dome came down in the earthquakes of 526–528 and was never replaced, so the court has stood open to the sky for fifteen centuries — far longer than it was ever covered.
What is not in dispute is the ambition. Taken together, the four basilicas and their octagon made the largest church in the Christian world, and it stayed the largest until Hagia Sophia was completed in Constantinople in 537.