Taq Kasra

On the Tigris plain south of Baghdad stands engineering's ancient high-water mark: Taq Kasra, the great iwan of Sasanian Ctesiphon, its single-span brick vault arcing about twenty-five metres wide and thirty-seven high - the largest unreinforced brick vault ever built, raised in the era when Ctesiphon ranked among the world's largest cities and Persia's kings held court beneath exactly this ceiling. The palace around it has returned to earth; the arch remains, partially restored across the last century, improbable and moving in equal measure. Visits from Baghdad pair it with Salman Pak's shrine town on the river's bend.

What you actually see

• The great vault - the 25-metre brick span, unmatched since antiquity.
• The facade wing - the surviving blind-arcaded front.
• The scale encounter - standing beneath the kings' ceiling.
• The Tigris bend - the river geography that raised a capital.

When to go

October to April for comfortable weather on the plain; late light warms the brick. Trips are arranged through Baghdad operators and depend on current conditions.

Honest expectations

Arrange through local partners and current advice as for everything in the country. The monument stands alone - context arrives via your guide's telling; conservation works may frame parts of the structure, in the good sense.

Nearby

Baghdad's museums and the Tigris towns.