help of local Muslims and only recovered by the Crusaders after they began to destroy the olive trees of Wadi Musa. The potential loss of livelihood led the locals to negotiate a surrender. The second is on the summit of el-Habis, in the heart of Petra, and can be accessed from the West side of the Qasr al-Bint. The ruins of Petra were an object of curiosity during the Middle Ages and were visited by Baibars, one of the first Mamluk sultans of Egypt, towards the end of the 13th century. 19th and 20th centuries The first European to describe them was the Swiss traveler Johann Ludwig Burckhardt during his travels in 1812. At that time, the Greek Church of Jerusalem operated a diocese in Al Karak named Battra (باطره in Arabic, and Πέτρας in Greek) and it was the opinion among the clergy of Jerusalem that Kerak was the ancient city of Petra. Burckhardt already spoke Arabic fluently, and was on his way to explore the Niger River when he heard stories of a dead city that held the tomb of the Prophet Aaron. He then became fascinated with finding the city. He then dressed himself up as a local, and only spoke in Arabic, bringing a goat with him with the intent of sacrificing it in honor of Aaron's Tomb. After one day of exploring, he was convinced that he had found the lost city of Petra. Léon de Laborde and Louis-Maurice-Adolphe Linant de Bellefonds made the first accurate drawings of Petra in 1828. The Scottish painter David Roberts visited Petra in 1839 and returned to England with sketches and stories of the encounter with local tribes, published in The Holy Land, Syria, Idumea, Arabia, Egypt, and Nubia. Frederic Edwin Church, the leading American landscape painter of the 19th century, visited Petra in 1868, and the resulting painting El Khasné, Petra is among his most important and well-documented. Missionary Archibald Forder published photographs of Petra in the December 1909 issue of National Geographic. Because the structures weakened with age, many of the tombs became vulnerable to thieves, and many treasures were stolen. In 1929, a four-person team consisting of British archaeologists Agnes Conway and George Horsfield, Palestinian physician and folklore expert Dr Tawfiq Canaan and Dr Ditlef Nielsen, a Danish scholar, excavated and surveyed Petra. The archaeologist Philip Hammond from the University of Utah visited Petra for nearly