Mystery Beach Sea Cave (中文版：神秘海灘海蝕洞) is a large beach-side cave in Yilan, Nan'ao Township. The cave is located 4.5km down Mystery Beach so to get there you either need to drive an offload vehicle, or walk about 1 hour. The beach is very remote, which makes it a great place to see the milky-way on a moonless night. There are dozens of sea caves along the beach, but this one is the largest. Due to the risk of falling rocks, it's recommended that you camp just outside the caves, rather than inside them. You can camp and swim anywhere.
Two hundred meters before the biggest cave is the Mystery Beach Waterfall. The waterfall flows directly onto the sand and into the ocean.
Mystery Beach Sea Cave
Yilan County, Nan'ao Township
Sea Cave: 24.40103, 121.78919
Parking (2wd cars/ scooter): 24.4355, 121.80105