The Marina Bay Sands is the world's most expensive hotel in Singapore, and with a world's largest outdoor pool at 55th storey.
"The infinity pool on the roof is in the 'SkyPark' which spans the three towers of the hotel. The platform itself is longer than the Eiffel tower laid down and is one of the largest of its kind in the world.
Infinity pools give the effect that the water extends to the horizon. In reality, the water spills over the edge into a catchment below, and is then pumped back into the pool."
[via]