A historic and archaeological city in Jordan, known as the Rose-Red City for the color of the rocks, established around the 6th century BC as the capital city of the Nabataeans, Petra was famous above all for two things: its trade and its hydraulic engineering systems. Petra is half-built, half-carved into the rock, and is surrounded by mountains riddled with passages and gorges. Impressive entrance called the Siq from a deep split in the sandstone rocks and at the end of the narrow gorge stands Petra’s most elaborate ruin, Al Khazneh (The Treasury), hewn into the sandstone cliff.