Melissani Lake is a stunning underground lake located on the island of Kefalonia in Greece. It is famous for its crystal-clear turquoise waters and unique geological formations. The lake is partially open to the sky, allowing sunlight to create a mesmerizing play of colors on the water's surface. Visitors can explore the lake by taking a boat tour, which offers a close-up view of the surrounding limestone cliffs and lush vegetation. The lake is also home to various species of fish and is a popular spot for photography and nature enthusiasts.