When were domes first built?

Domes were first built in ancient times, with one of the earliest examples being the dome of the Pantheon in Rome, completed around 126 AD. However, the concept of domes can be traced back even further, with structures like the ancient Mesopotamian ziggurats and the use of dome-like forms in early Egyptian architecture. The development of domes continued through various cultures, evolving in design and materials over the centuries.