An indoor pool claiming the mantle of world's larges isn't open to the public. It's run by NASA and is called the Neutral Buoyancy Lab, NBL. The NBL helps train astronauts to move in a weightless environment, because swimming underwater in SCUBA gear is similar to weightlessness. The pool is, according to NASA, "62 meters -- 202 feet -- long, 31 meters -- 102 feet -- wide and 12 meters -- 40 feet -- deep." It contains a model of the International Space Station that is the same size as the one orbiting the earth.
SCUBA divers in Belgium have the benefit of the world's deepest indoor pool. NEMO 33 is 33 meters, more than 100 feet deep. It's used primarily as a location to train SCUBA divers, but recreational divers hang out here, too. It's filled with non-chlorinated, filtered spring water, and there are simulated caves at the bottom.
The largest indoor wave pool in North America can be found in the West Edmonton Mall in Alberta, Canada. This behemoth features 17 water slides and bungee jumping. It's something of an oasis in frosty Canada. The pool is kept at a tropical 86 Fahrenheit.
Running the world's biggest swimming pool must be expensive, because as of 2007, the world's largest indoor pool was closed. Seagaia Ocean Dome, located in Miyazaki, Japan, was 100 meters wide and 300 meters long. A ferris wheel, and sandy beach gave it a tropical feel. Surfers could hit the waves every 20 seconds, though the pool's concrete floor was something of a deterrent. The pool featured a retractable roof -- clouds were painted on it so that when closed, swimmers had the feel of being outside on a cloudy day. The big drawback: The pool was located pretty close to the beach.
