Grotte di Nettuno (Neptune's Caves)
The cave was discovered by local fishermen in the 18th century and has since developed into a popular tourist attraction. The grotto gets its name from the Roman god of the sea, Neptune.
The combined length of the cave system is estimated to be around 4 kilometers, but only a few hundred metres are accessible to the public. Inside are passages of lit stalactite and stalagmite formations, and a 120-metre-long saltwater lake, which is at sea level. The cave was once a habitat for the Mediterranean Monk Seal, which has become extinct in the area.
You can access the caves from the top of Capo Caccia by 656 stairs descent or by boat, only when the sea is calm enough to allow disembarking.
Read more at www.grottadinettuno.it
To avoid overcrowding in Summer, you have to make a reservation at least 24 hours in advance to visit the cave.
You can book the visit at https://www.algheroexperience.it/prenotazione-grotta-nettuno-alghero.html
The tours start every hours during opening time (for example 10 AM, 11 AM, etc.) For further information and opening times, you can check the official web site https://grottadinettuno.it/orari/
The visits may be canceled in case of bad weather as the cave could be closed for safety reasons