Neptune's Grotto is a stunning sea cave located near the town of Alghero in Sardinia, Italy. It is famous for its impressive stalactites and stalagmites, formed over thousands of years. The grotto can be accessed by boat or through a staircase of 654 steps carved into the cliffside. The cave is named after Neptune, the Roman god of the sea, and features a large underground lake. Visitors can explore the grotto's unique rock formations and enjoy the beautiful reflections in the water. It is a popular tourist destination, attracting nature lovers and adventure seekers alike.