The origins of the town of Terracina are lost to time, as the area was probably inhabited for many centuries even before the Romans conquered it during the fifth century B.C.
On the hill overlooking the town, the first known constructions were erected in the 3rd century B.C., and maybe consisted of just a small sanctuary. In the early first century B.C., a large monumental complex rose on the hill. The complex contained the new larger temple and a military camp to control the nearby Via Appia, an important road connecting Rome to southern Italy. The area was surrounded by defensive walls. The temple is attributed to Jupiter Anxur, with Anxur being both the ancient Volscian name of the town and the name of Jupiter as a youth.
During the Middle Ages the complex was burned down and destroyed, and the area was abandoned for centuries before becoming a monastery. New walls and other defensive structures, dated to around the 13th century, suggest that the ruins of the Roman complex were used as a military camp. The area was again abandoned in the 16th century, but was found and excavated starting in the late 19th century.