The largest swimming pool in the world is the sea water Orthlieb pool in Casablanca, Morocco. It is a saltwater pool and is 480m (1575 ft) long and 75m (246 ft) wide with an area of 3.6 hectares (36,000 sq m).
The pool is 480 meters or 1,574 feet long and 75 meters or 246 feet wide. The Orthlieb Pool is filled with sea water and covers a soggy 8.9 acres.
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Also this, in Garden City, Kansas: The 'Big Dipper' as it was called in 1922 when it was first built, is a very large pool. When all the adjectives are added, it is the 'largest outdoor, concrete, free, municipal pool in the world'. The pool measures 220 feet by 330 feet, roughly the size of a football field. As a promotion for a post card many years ago, a motor boat was placed on the water and pulled a water skier around the pool! Large as it is, it is not the world's largest pool. There are others that are larger. We are the world's largest free swimming pool in the world. The pool holds approximately 2.6 million gallons of water.