The area around Petra has been inhabited from as early as 7000 BC, and the Nabataeans might have settled in what would become the capital city of their kingdom as early as the 4th century BC. Archaeological work has only discovered evidence of Nabataean presence dating back to the second century BC, by which time Petra had become their capital. The Nabataeans were nomadic Arabs who invested in Petra's proximity to the incense trade routes by establishing it as a major regional trading hub. Pliny the Elder and other writers identify Petra as the capital of the Nabataean Kingdom and the centre of their caravan trade.
Enclosed by towering rocks and watered by a perennial stream, Petra not only possessed the advantages of a fortress, but controlled the main commercial routes which passed through it to Gaza in the west, to Bosra and Damascus in the north, to Aqaba and Leuce Come on the Red Sea, and across the desert to the Persian Gulf. In AD 106, when Cornelius Palma was governor of Syria, the part of Arabia under the rule of Petra was absorbed into the Roman Empire as part of Arabia Petraea, and Petra became its capital. The native dynasty came to an end but the city continued to flourish under Roman rule. It was around this time that the Petra Roman Road was built.
A century later, in the time of Alexander Severus, when the city was at the height of its splendor, the issue of coinage came to an end. Meanwhile, as Palmyra grew in importance and attracted the Arabian trade away from Petra, the latter declined. Another Roman road was constructed at the site. This road followed the old routes of Nabataean caravans.
In 125 AD, one of Emperor Hadrian's administrators left marks in Petra, pointed out by documents found at the Dead Sea. In 130 AD, Hadrian visited the former Nabataean capital, giving it the name of Hadriane Petra Metropolis, imprinted on his coins. The interest that Roman emperors showed for the city in the 3rd century suggests that Petra and its environs remained highly esteemed for a long time. An inscription to Liber Pater, a god revered by Emperor Septimius Severus, was found in the temenos of the temple known as Qasr al-Bint, and Nabataean tombs contained silver coins with the Emperor's portrait, as well as pottery from his reign.
Emperor Elagabalus declared Petra to be a Roman colony, when he reorganised the Roman Empire towards the end of the 3rd century. The area from Petra to Wadi Mujib, the Negev, and the Sinai Peninsula were annexed into the province of Palaestina Salutaris. Petra may be seen on the Madaba mosaic map from the reign of Emperor Justinian.
