World's largest pool which cost $1bn and holds 66m gallons.

World's Largest Pool holds 66m Gallons

At the San Alfonso del Mar resort in Chile, a world's largest pool which cost $1bn and holds 66m gallons. It also hold the Guinness record for the world's deepest - so if you don't feel like diving 115ft to the bottom, it might be best to bring some spare goggles.

The pool opened in December 2006 after nearly five years of construction work and is said to have set developers back as much as £1billion. And on top of that eye-watering initial cost, it takes a further £2million a year to keep it in working order.

Swimming a length in this, the world's largest outdoor pool, would mean stroke after stroke for more than three fifths of a mile - that's 20 Olympic-size swimming pools.

World's Largest Pool in Chile

Apart from its large size, the lagoon has another spectacular feature: its waters have the transparency and intense turquoise color of tropical seas. This has been made possible thanks to an advanced technology developed by the Chilean company Crystal Lagoons, which uses water pumped from the Pacific Ocean, that is then filtered and treated for supply to the pool, built at the cost of US$3.5 million whilst the maintenance costs are said to be 1/4th of those associated to a pro golf course.

1,000m long, 19-acre outdoor pool, 250 million liters of water which holds a Guinness world record as the largest in the world.