The ancient city of Petra is situated in southwest Jordan, between the Dead Sea and the Red Sea, 262 km south of Amman near the modern-day town of Wadi Musa. It is noted for its monumental rock-cut architecture and for surrounding sandstone cliffs with many passageways and gorges. Petra is typically approached from the east through a narrow gorge known as the Siq (Wadi al-Siq).

The site has been occupied since ancient times, with Paleolithic and Neolithic remains discovered there. Petra served as the capital of the Nabataean (312 BCE-106 CE) empire, when it underwent a period of intense urban development, flourishing as a center of the spice trade. During this time, the main street in Petra was paved, public buildings other facilities were constructed, and tomb facades became monumental. An extensive hydraulic system including dams, cisterns, rock-cut water channels, and ceramic pipes was also established by the Nabataeans. Many of the most impressive public buildings at Petra can be dated to the Nabataean ruler Aretas IV (r. 9 BCE-40 CE), including the main theater, the Temple of Dushara (Qasr Bint Fir'wan), the Temple of Allat, and possibly the the treasury (Khaznat al-Fir'awn) and Al-Dayr, one of the best known rock-cut tombs.

In 106 CE Petra was incorporated into the Roman province of Arabia by emperor Trajan (r. 98-117 CE), which appears to have had little effect on its architecture, except for the renovation of the theater. Under the Romans, Petra continued to flourish until changing trade routes brought about its decline, and after earthquakes in 363 and 551, continuous habitation in the city seems to have ceased. During the Crusades in the 11th-12th centuries it was known as the Valley of Moses. After the fall of Jerusalem in 1187 Petra fell into obscurity, until it was discovered by the Swiss explorer Jean-Louis Burckhardt in 1812.

The earliest survey of the monuments was carried out in 1897-1898 by Rudolph E. Brunnow and Alfred von Domaszweksi, who numbered, described, and photographed over 800 structures. Of those, 523 were identified as funerary, including the rock-cut facade tombs. The first excavation of the site began in 1929 by George Horsfield. The funerary architecture of Petra is what is now most apparent, with tombs facades carved throughout the sandstone cliffs, including the ensemble known as the Royal Tomb group along the western face of the mountain ridge that forms Petra's eastern boundary. Few private houses have been excavated. Public architecture includes the hydraulic system, temples, and the main theater.

Sources:

Hammond, Philip C. "Petra." Grove Art Online. Oxford Art Online. Oxford University Press, accessed January 12, 2015, http://www.oxfordartonline.com/subscriber/article/grove/art/T066760.

"Petra." Encyclopædia Britannica Online. Accessed January 12, 2015, http://academic.eb.com/EBchecked/topic/454080/Petra.

UNESCO. "Petra." Accessed January 12, 2015, http://whc.unesco.org/en/list/326.