The patron saints of Sperlonga are Saint Leo the Great, the town's protector, and Saint Roch, co-patron: the feast is held in the days before and after the first Sunday of September, in the church of the Madonna Assunta, the only parish in the whole municipality. The two processions cover almost the entire territory, both the upper town and the seaside one; particularly distinctive is that of Saint Roch, which reaches the sea in the evening, where fireworks are set off, before returning to the historic centre.
The name Sperlonga likely comes from the large grotto (spelunca) built into the villa of the Roman emperor Tiberius, an expansion of an earlier late-Republican villa: the natural cave, known to archaeologists since 1908, had been turned into a summer dining room with water features, decorated with extraordinary sculptural groups from the Ulysses cycle, including the colossal Polyphemus Group, found in fragments in 1957 and now kept in the town's national archaeological museum. In the 6th century the ruins of the imperial villa were used as a refuge, but the town developed on the nearby San Magno promontory, in defence against Saracen raids from the sea.
