Petra is the story of water and trade. It was constructed in the 1st century BCE by the Nabateans who likely migrated to the area from modern day Yemen. They were skilled hydrologists and made their fortune trading bitumen mined from the Dead Sea to Egypt. They also established and provided protection along the main trade route through the Arab peninsula, a service for which they charged 10% of the cargo – mostly frankincense and myrrh which at the time was worth its weight in gold. To protect their wealth and their people, the Nabateans carved their city out of the sandstone rocks in modern day Jordan.