Petra is a historical and archaeological city in the Jordanian governorate of Ma'an that is famous for its rock cut architecture and water conduit system. Established sometime around the 6th century BC as the capital city of the Nabataeans, it is a symbol of Jordan. It lies on the slope of Mount Hor in a basin among the mountains which form the eastern flank of Arabah (Wadi Araba), the large valley running from the Dead Sea to the Gulf of Aqaba. Petra has been a UNESCO World Heritage Site since 1985 and is one of Seven Wonders of the World. More info in Wikipedia.