Sharpn: History — Sharpen your mind

Ctesiphon and the Great Arch

Persia: Empire and Afterwards

The Capital on the Tigris

Ctesiphon, on the Tigris a little south of where Baghdad would later stand, was the Sassanid capital and among the largest cities on earth. It was taken by Roman armies more than once and always recovered. Its position mattered: whoever held it controlled the richest agricultural land between the rivers and the road east.

The Vault

The Taq Kasra — the great arched hall — still stands, and it is difficult to believe when you see it. A single brick vault, parabolic rather than semicircular, roughly thirty-seven metres high and twenty-six metres across at the base, built without any supporting framework beneath it. Bricklayers laid it in leaning courses so that each ring supported itself as it went up. It is the largest single-span brick vault ever built in the ancient world, and it has stood for about fifteen hundred years.

The Iwan

Its form is a Persian invention with a long future: a vaulted hall, enormous, open along one entire side. The iwan gave audiences a stage — the king seated in the depth of the vault, the court and petitioners in the open. After the Islamic conquest, the same form was absorbed into mosque architecture and spread from Central Asia to India, which is why the great courtyards of Isfahan, Samarkand and Delhi all have those vast open-fronted vaults facing inward.

The City That Fed Baghdad

When the Abbasids founded Baghdad in 762, they built about thirty kilometres away, and Ctesiphon was quarried for material. Some of the new capital of the Islamic world was physically made of the old capital of the Sassanid one — and the Abbasid court adopted Sassanid ceremony, administration and titles along with the bricks.

What Survives

The hall remains, part of one flanking wall collapsed, standing alone on a plain in modern Iraq. Everything else — the palaces, the city, the population of a great capital — is gone. What is left is the single most impressive piece of engineering the Sassanids attempted, and they got it right.

Key Dates to Remember

1st c. BC — Ctesiphon becomes a royal capital under the Parthians
3rd–6th c. AD — Sassanid capital; the Taq Kasra is built
637 AD — Taken by Arab armies
762 AD — Baghdad founded nearby; Ctesiphon quarried for material

Fun Fact: The Taq Kasra was raised without any supporting framework beneath it — bricks laid in leaning courses so each ring held itself up. It is the largest brick vault of the ancient world and has stood about fifteen hundred years.