Nemo 33 is a recreational diving centre located in Brussels, Belgium that houses the deepest pool in the world. The deepest part of the pool measures at 33m (108 feet) which is a circular pit used for diving instruction.

Unlike other conventional pools, this pool is filled with 2.5 million litres of non-chlorinated spring water maintained at 30°C and comes with simulated caves at the 10m mark. Visitors can also look into the pool at various depths through underwater windows.

via anvari

Here are some videos taken at the facility found on Youtube: