Not only is the Nemo 33 swimming pool in Brussels, Belgium the deepest indoor swimming pool in the world, but in our minds, it’s also the creepiest. Seriously, who wants to take a swim down a black hole for fun? Oh wait…the pool is actually designed for divers to practice their skills (this makes the pool less creepy but we’re still terrified to venture anywhere near it. Claustrophobia, anyone?!). John Beernaerts came up with the idea for Nemo 33 in 1996, and in May of 2004, the pool finally opened it’s doors to the public. The Guinness World Records states:

The Nemo 33 diving pool has a depth of 33 meters (108 ft) at its deepest point and contains around 2.5 million litres (550,000 gal, 4.4 million pints, 660,000 US gallons) of water. The facility, which opened in June 2004, is used for dive training, leisure diving, and research.

The water is kept at a constant 30 degrees Celsius (86 degrees Fahrenheit) thanks to a large array of solar panels. There are two ‘basins’ and three ‘pits’, the deepest of which is 6 m (19 ft 7 in) across and drops to 33 m (108 ft). There are underwater ‘caves’ for exploration and three air-filled diving bells that enable diving instructors to communicate with their charges without returning to the surface.
Pretty cool, actually. The idea of make-belief underwater caves seems like a great idea for diver training and classes. Nemo 33 offers diving classes to anyone over the age of 12 years, and at a reasonable price, too.