There are in fact three ponds on Vallisaari: one larger pond, the small Kluuvilampi Pond and a small man-made pond. In the Middle Ages Vallisaari was called “Pond Island”, since its pond was vital to seafarers, as the only place along shipping routes where they could get plenty of drinking water. In the 1950s, when many people lived on Vallisaari, the pond was used in many ways. People swam here, dived into the water from a tower, sunbathed on the shore, washed their clothes here, and pumped washing water from the pond. The pond has more recently been left to nature, and it is home to water creatures including small crayfish.