Each ancient civilisation had its own distinct architecture. Egypt built pyramids and Rome had coliseums. For the Mesopotamian civilisation – modern day Iraq – that distinctive structure was the ziggurat.
At the end of the fourth millennium BC, these enormous mud-brick platforms were built at numerous sites in Mesopotamia.
Today, ziggurats are found scattered around Iraq and Iran, and were used for religious rituals and administrative purposes.
One of the largest and best-preserved ziggurats of Mesopotamia is the Great Ziggurat at Ur, built about 2100 BC. Ahead of a visit by Pope Francis, the structure is being illuminated to show off its magnificence.
Small excavations and renovations occurred at Ur's ziggurat when a project jointly sponsored by the British Museum and the University of Pennsylvania Museum under the direction of Sir Leonard Woolley began at the site.
Sir Woolley used ancient descriptions and representations of ziggurats to reconstruct the upper stages that were destroyed over the centuries. The Iraqi Directorate of Antiquities has since restored its lower stages.
A look around the ancient city of Ur – in pictures
