Neptune's Grotto, Sea cave in Alghero, Italy.
Neptune's Grotto is a sea cave beneath Capo Caccia with a series of chambers extending deep into the limestone. A large saltwater lake called Lamarmora forms the centerpiece of this underground landscape, surrounded by mineral deposits and rock formations.
A local fisherman found the cave entrance in the 1700s, but access remained limited to those arriving by sea for many years. The construction of the Escala Cabirol staircase carved into the cliff in 1959 made the cave reachable on foot.
The name references Neptune, the Roman god of the sea, reflecting the deep connection between this place and the ocean. Throughout the chambers, stalactites and stalagmites create a natural cathedral-like setting that visitors walk through.
You can descend via a staircase carved into the cliff or take a boat from Alghero's port when weather permits. The stair route offers views of the sea from above, while the boat trip brings you closer to sea level before entering.
Below the main chambers lies a submerged section with additional caverns extending underwater. The largest of these hidden spaces is called Nereo Cave, forming part of a drowned karst landscape that few visitors ever see.
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