# Hagia Sophia Dome

> The great dome of Hagia Sophia in Istanbul, built 532-537, rebuilt after a collapse in 558 and repaired after further failures in 989 and 1346.

- URL: https://roof.wiki/hagia-sophia-dome/
- Topic: History of Roofing
- Also known as: Aya Sofya dome; Hagia Sophia
- Regions: Europe, Middle East
- First published: 2026-11-02 · Last reviewed: 2026-11-02
- Cite as: "Hagia Sophia Dome." roof.wiki. https://roof.wiki/hagia-sophia-dome/

## Key facts

- **Built:** 532-537
- **Architects:** Anthemius of Tralles, Isidore of Miletus
- **Rebuilt dome completed:** 562
- **Dome diameter:** About 32.7-33.5 m (107-110 ft)
- **Interior height:** About 55.6 m (182 ft)

**Hagia Sophia** in Istanbul (ancient Constantinople) was built for the Byzantine emperor **Justinian I** between **532 and 537**. Its vast central dome, seemingly floating above a ring of windows, was the largest of its time and set the model for Byzantine and later Ottoman domed architecture.

## Design

The architects were **Anthemius of Tralles** and **Isidore of Miletus**. Their key structural device was the **pendentive**: curved triangular sections of masonry that make the transition from the square plan of four great piers to the circular base of the dome. Semi-domes to the east and west extend the covered space.

## Collapse and rebuilding

The first dome proved too flat. Earthquakes in 553 and 557 cracked it, and in **558** part of the structure, including the eastern semi-dome, collapsed. **Isidore the Younger** rebuilt the vault about 6.25 m (20.5 ft) higher using lighter materials, as a ribbed dome on pendentives with a diameter of about 32.7-33.5 m (107-110 ft). The reconstruction was completed in **562**. The interior height reached about 55.6 m (182 ft).

## Later failures

- **989:** an earthquake brought down the western dome arch. The Armenian architect **Trdat** rebuilt the west side with 15 dome ribs; the church reopened on 13 May 994.
- **1346:** cracks from an earthquake in October 1344 led to partial collapses on 19 May 1346. Repairs by Astras and Peralta began in 1354.

## Roof covering

The dome's outer covering has been repaired many times. In the 20th century cracking of its copper roof contributed to deterioration that prompted international conservation funding, including grants from the World Monuments Fund.

## Status

Hagia Sophia is part of the UNESCO World Heritage Site "Historic Areas of Istanbul", inscribed in 1985.

## Significance

The building showed how a large dome could be raised over a square plan, a problem central to later church and mosque roofing. Its repeated collapses also made it an early, well-documented case study in the effects of earthquakes on masonry roofs.

## Sources

1. Hagia Sophia — Wikipedia. https://en.wikipedia.org/wiki/Hagia_Sophia
2. Historic Areas of Istanbul — UNESCO World Heritage Centre. https://whc.unesco.org/en/list/356