A rather large swimming pool at a hotel in Chile:
Link to google maps:
The lagoon employs cutting-edge technology that allows it to "harvest, filter and permanently recirculate ocean water", according to biochemist and businessman Fernando Fischmann, who heads Crystal Lagoons Corporation, the company that designed the mammoth pool.
The San Alfonso pool:
* Is 1000m long (should get a good 500m speed run in there)
* Is 8 hectares in surface area or the equivalent of 6,000 standard-size 8-metre-long swimming pools.
* It easily dwarfs the next biggest pool - the Orthlieb in Casablanca, Morocco - which measures 150m x 100m.
* The lagoon's water temperature in summer is 26C, nine degrees warmer than the ocean it sits alongside.
* Its waters are transparent to a depth of 35 metres.
* It cost approximately US$1.5 billion to build and about US$4m per year in maintenance.