The lost city of Petra is an archaeological site in Jordan, lying 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. It is famous for having many stone structures carved into the rock. Petra was chosen as one of the New Seven Wonders of the World in 2007 and a World Heritage Site since 1985.

According to Arab tradition, Petra is the spot where Moses struck a rock with his staff and water came forth, and where Moses' brother, Aaron, is buried, at Mount Hor, known today as Jabal Haroun or Mount Aaron. The Wadi Musa or "Wadi of Moses" is the Arab name for the narrow valley at the head of which Petra is sited. A mountaintop shrine of Moses' sister Miriam was still shown to pilgrims at the time of Jerome in the 4th century, but its location has not been identified since.

The Monastery, Petra's largest monument, dates from the 1st century BCE. It was dedicated to Obodas I and is believed to be the symposium of Obodas the god. This information is inscribed on the ruins of the Monastery.

Petra declined rapidly under Roman rule, in large part due to the revision of sea-based trade routes. In 363 an earthquake destroyed many buildings, and crippled the vital water management system. The ruins of Petra were an object of curiosity in the Middle Ages and were visited by Sultan Baibars of Egypt towards the end of the 13th century. The first European to describe them was Johann Ludwig Burckhardt in 1812.

Because the structures weakened with age, many of the tombs became vulnerable to thieves, and many treasures were stolen. The site suffers from a host of threats, including collapse of ancient structures, erosion due to flooding and improper rainwater drainage, weathering from salt upwelling, improper restoration of ancient structures, and unsustainable tourism. The latter has increased substantially ever since the site was named one of the New Seven Wonders of the World in 2007.