Madā'in Ṣāliḥ or Hegra, also called Al-Ḥijr, is an ancient city located in the northern part of the Hejazi region of Saudi Arabia, about to the north of Riyadh. Madā'in Ṣāliḥ is considered to be one of the most important and oldest ancient cities in the country. Madā'in Ṣāliḥ lies to the northwest of the city of AlUla, in a strategic position on one of the most important ancient trade routes, which linked the south of the Arabian peninsula to the north, as well as to the great economic and cultural centres of Mesopotamia, Syria and Egypt. It was the second-largest city in the kingdom of the Nabateans. The Nabateans were a group of Arab tribes whose economy was based on pastoralism, and over time they settled, created and developed several cities and become traders. The Nabataeans occupied a territory in the south of the area of Ash-Shām where they founded the Nabataeans; their capital was Petra in Jordan, which was chosen as one of the Seven Wonders of the World in 2007. Their language was a form of old northern Arabic. The landscape of Madā'in Ṣāliḥ is characterized by impressive rock formations, sandstone hills of varied colours, from red to yellow and white. The area of Madā'in Ṣāliḥ covered by the site is about . The tombs are distributed in groups of various importance, as follows: