The deepest pool in the world is known as Nemo 33, a recreational scuba diving center located near Brussels, Belgium which opened in 2004.

It is filled with 2,500,000 liters of non-chlorinated, highly filtered spring water maintained at 30 °C (86 °F) and contains several simulated underwater caves at the 10 m depth level.

It is built with several platforms and a 33-meter (108 ft) deep cylindrical pit (deeper than you are allowed to go on a standard SCUBA diving license).

“There are numerous underwater windows that allow outside visitors to look into the pools at various depths. The complex was designed by Belgian diving expert John Beernaerts as a multi-purpose diving instruction, recreational, and film production facility.” Via Toxel

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