Settled as early as 9,000 BC, Petra was made the capital of the Nabataean Kingdom sometime around the 4th century BC. Over the following years, the city flourished as a trade hub, reaching a population of 20,000 by 100 AD. As trade took to the seas, the city declined, and though several Byzantine churches were built here, it was abandoned by the early Islamic era, and only used by nomads until its rediscovery in 1812. Today, the network of temples, tombs, and churches hand-hewn into the cliff are a breathtaking sight, blending raw-beauty and human artisanship. And though not as glamorous, the city’s water system is a feat of engineering. While the most iconic building, the treasury, is the first thing visitors see after walking through the 1.2-kilometre-long gorge to reach the city, Petra covers nearly 100 square miles, and can easily take a few days to fully explore.