Surrounded by fantastically shaped rocks and only accessible by a skinny bridge arching over the waves, this retro underwater observation tower would make the perfect lair for a sea-loving villain.

This old-school marvel was built in 1972, and was once a major tourist attraction for both visitors and locals, who came to climb down into the foot of the tower to see fish, sea turtles, mantas (and the occasional lobster) swimming by the porthole windows. No animal cruelty here, as the sea creatures come and go as they please, making for a rather meditative experience for the visitors who continue to drop by today.

The red and white cross-shaped tower is one of the most unusual spots in Ashizuri-Uwakai National Park, and is apparently also one of the few remaining buildings of its kind in Japan. Nearby you can also take glass boat rides to see the flourishing coral and walk on the wild coastlines.