Hatra was a caravan city in the northern Iraqi desert, ringed by two circular walls and more than 160 towers. Inside the temenos, barrel-vaulted iwans rose thirty metres in dressed limestone and grey alabaster, their walls hung with relief slabs cut in strict frontality — figures facing straight out, Greek arches standing beside Mesopotamian and Arab gods.

This system takes the stone at face value. Warm pale ashlar for the ground, carved-shadow grey for structure, and the surviving pigment — red, black, the ground of a lost gilding — used sparingly, the way it survives: only down in the cut.