The Grotto Di Nettuno, or 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 a steep staircase of 654 steps or by boat, offering visitors breathtaking views of the surrounding coastline. Inside the grotto, visitors can explore various chambers filled with crystal-clear waters and unique rock formations. The cave is also home to a variety of marine life, making it a popular spot for both tourists and nature enthusiasts.