Nemo 33
A 34.5-metre freshwater shaft in Uccle that held the Guinness record as the world's deepest indoor pool for a decade.
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Designed by Belgian diving expert John Beernaerts in 2004 as a dive instruction and film production facility, this 2.5-million-litre pool keeps its spring water at a steady 30°C via solar heating — warm enough that divers skip the dry suit. Non-divers can watch through underwater windows at multiple depths. It lost the world record in 2014 to Italy's Y-40, but at 34.5 metres it remains among the deepest anywhere.
What to look for
- Simulated underwater caves at the 10-metre level
- Underwater windows where spectators outside the pool can watch divers at depth
- The full 34.5-metre column of non-chlorinated spring water visible from above
Open to tourists and amateur divers aged 12+; every diver must be certified or trainer-supervised and enter with a certified dive buddy.
Nemo 33 is one of 33 sights worth the detour in Brussels, all bundled offline in Voyage GO — download the Brussels pack and it sits on your map with no signal, filling your travel passport the moment you walk past.
More to see in Brussels
- Manneken PisA 55.5 cm bronze boy that somehow became the face of an entire country — the joke is entirely intentional.
- Grand-PlaceEvery guildhall surrounding you was rebuilt from rubble — French artillery levelled the square in 1695, and the Town Hall tower survived only because it was the gunners' aiming point.
- AtomiumNine stainless-steel spheres arranged as an iron crystal blown up 165 billion times — built to headline a World's Fair and never taken down.
- Stoclet PalaceA UNESCO World Heritage house you can only see from the pavement — by design, and by the owner's choice.
- King Baudouin StadiumInaugurated for Belgium's 100th birthday in 1930, this 70,000-seat bowl on the Heysel Plateau hosted six European finals — and the night football changed forever.
- Cathedral of St. Michael and St. GudulaBelgium's national church began as a chapel on a trade-route crossroads in the 9th century — eleven centuries of building decisions are now stacked on a hill called "Mount of Sorrow."