First mentioned in 6th century BC the area is UNESCO World Heritage Site and Ramsar Wetland site. Successive peoples have inhabited the site, each one adapting and developing the architecture. The round theatre was dedicated to the healing god of Asceplus (4th century BC). The Roman bathhouse with its hypocaust-heating (2nd century AD). An early 6th century AD baptistery which is the largest free-standing Byzantine baptistery in the world. The Great Basilica, and early Christian church constructed in 6th century AD. A remarkable microcosm of history.