The Romans conquered much of the Levant in 63 BC, inaugurating a period of Roman rule that lasted for four centuries. In the northern modern-day Jordan, the Greek cities of Philadelphia (Amman), Gerasa, Gedara, Pella and Arbila joined with other cities in Palestine and Syria; Scythopolis, Hippos, Capitolias, Canatha and Damascus to form the Decapolis League, a fabled confederation linked by bonds of economic and cultural interest. Philadelphia became a point along a road stretching from Ailah to Damascus that was built by Emperor Trajan in 106 AD. This provided an economic boost for the city in a short period of time.