Brussels is Nemo 33 - the deepest indoor swimming pool in the world.
It is designed specifically for diving, and came up with his John Beernarts in 1996.
Nemo 33 - a pool depth of 33 meters
Opened in 2004, the pool is used for training divers to various studies, as well as for recreation.
The water temperature is constantly kept at around 30 degrees due to the large number of solar panels.
The pool has two "reservoir" and three "pit", the deepest of which is 6 m in diameter and reaches a peak in the 33 m pool.
The pool also has underwater "cave" for research.