Sperlonga is a small settlement entrenched around the top of the rocky headland of Monte Magno, jutting out to sea. The village owes its name to the large natural grotto or spelunca that opens out on this coastline. It is where the Emperor Tiberius decided to build his holiday residence and the cave is in fact known as Tiberius' Grotto. A National Archaeological Museum was built nearby along the Via Flacca to house the findings from the cave and is visited by many tourists, in particular by foreigners. The history of mediaeval Sperlonga is that of a small fishing village often forced to face attacks from the sea, such as the Saracen raids. In order to create a defensive line, four towers were built: the Torre Centrale, now undistinguishable from the village buildings, the Torre del Nibbio, the Torre Truglia at the entrance to the small harbour, and the Torre Capovento. For centuries Sperlonga was cut off from the main communication roads and so kept its natural environment intact. It can boast one of the cleanest waters in the Lazio region and has been awarded the prestigious European Blue Flag for the pureness of the water for four consecutive years.