Incredible! Largest Swimming Pool in the World. San Alfonso del Mar,Chile -- A one kilometre long swimming pool in Chile. Try making a splash in the world's largest swimming pool. San Alfonso del Mar resort in Algarrobo, Chile, has the largest swimming pool in the world. It's 3324 ft (1015 m) long. Tourists sail a boat in the world's largest swimming pool at a seaside resort in Algarrobo, Chile.