Neptune's Grotto is a stunning stalactite cave located near the town of Alghero on the island of Sardinia, Italy. It was discovered by local fishermen in the 18th century and has since become a popular tourist attraction. The cave gets its name from Neptune, the Roman god of the sea. To reach the entrance, visitors can either take a 654-step stairway cut into the cliff or hop on a short boat trip from the port of Alghero. Inside the cave, there are illuminated pathways that lead visitors through breathtaking stalactite and stalagmite formations, as well as a saltwater lake. It's a must-visit spot for nature enthusiasts and those seeking a unique underground adventure.