Lake Mashū is a stunning crater lake located in Hokkaido, Japan, known for its crystal-clear waters and mysterious fog that often shrouds its surface. Formed in the caldera of a potentially active volcano, this lake has no significant inlets or outlets, making it one of the clearest and deepest lakes in Japan. Visitors can enjoy the scenic Mashu-dake Hiking Course, which offers breathtaking views of the surrounding landscape. With its unique beauty and tranquil atmosphere, Lake Mashū is a must-visit destination for nature lovers and adventure seekers alike.