The origin of the wealth of Petra was in the caravan trade. Up to seven routes converged in the desert city, where products were distributed to Alexandria, Jerusalem, Damascus, Apamea and many other cities. Literary sources such as Periplus of the Erythraean Sea and Pliny, detailing the enormous rates at which the goods were subject circulating through the Nabataean kingdom. Figures are given up to 25 or 50 percent of taxation. This burden, coupled with the high value of marketed products, such as silk, shoe polish, incense, spices and myrrh, and the huge number of displaced goods allow us to understand the sudden splendor of the Nabataean kingdom, caused by the huge demand derived from the Pax Romana , which is embodied in his wonderful capital. On the chronology of the Nabatean kingdom no direct data are available that allow drawing a more or less firm history. We have to conform with the archaeological and isolated news provided by classical sources, essentially Diodorus, Strabo and Josephus. All documentation reveals that the middle of the second century BC there was a royal family in Petra, attested by Strabo, but the monarchy may have preceded the dynasty of Aretas I, traditionally considered the first Nabataean king, Aretas I name is mentioned in the oldest Nabataean inscription from 168 BC From that time the structures were consolidated the kingdom and began to build the royal necropolis. The various kings compete with each other to achieve more and more beautiful facades and spectacular for their tombs carved into the rock walls.