What were ziggurats for, and could anyone climb them?

A ziggurat was a house for a god, built as a giant staircase of bricks. It is a massive terraced structure of successively smaller levels, built in ancient Mesopotamia and Iran. The Sumerians believed the gods lived in the temple at the top, so only priests and other highly respected people could enter. Ziggurats were not places for public worship or ceremonies. Each city had its own patron god, and the priests who were allowed up the stairs had the job of caring for that god and attending to its needs.

The oldest idea behind them is simple: raise the temple. Before ziggurats there were raised platforms from the Ubaid period, in the sixth millennium BCE, and ziggurats began as platforms. The simplest example is the White Temple of Uruk, set on a base whose purpose was to bring the temple closer to the heavens and give access by steps. The Mesopotamians believed these pyramid temples connected heaven and earth, and the ziggurat at Babylon, Etemenanki, means "House of the foundation of heaven and earth".

Their bricks tell the story: sun-baked bricks formed the core, covered by a skin of fired bricks that was often glazed in different colours, and sometimes engraved with a king's name. They had between two and seven levels. The famous Great Ziggurat of Ur was built by King Ur-Nammu, who dedicated it to the god Nanna around the 21st century BC.

There was also a practical side. A high platform let priests escape the water when rivers flooded the lowlands, and with only three stairways, a few guards could stop outsiders from watching the rituals at the top.

Even the shrine at the top is uncertain. Archaeologist Harriet Crawford points out that the only evidence for it comes from the Greek writer Herodotus and that physical proof is non-existent. A shrine on top is a working hypothesis, not a certainty.