The Green cave is situated at the far end of the western bay of Porto Conte in the eye-catching promontory of Capo Caccia, where you can also visit the most popular "Neptune Cave". It’s about 45 kilometres from Alghero and it’s possible to get there taking the SS 127-bis. If you’re interested in an excursion to the cave it’s advisable to contact the spelaeologists’ staff of Alghero since its entrance, placed 75 metres above sea-level, may be unsafe. The inside of the cave looks like a huge Karst cavity with calcareous walls dated back to 200 millions years, where you can see stalagmites, a small salt lake lying in several rooms, which were once prehistoric men’s dwelling.

Some prehistoric graffiti are still visible on the walls. It is made certain that this cave was used by man from the Neolithic to the Christian Age; mainly it was a site of worship and cult of the dead. Proof of this are some recent findings, such as round-shaped pottery items made with clay and painted with red dyes.