Waterworld

One of Singapore's popular spots to rest and exercise is a vast green park near the mouth of the Marina Channel. On late afternoons, residents can be seen jogging around the area or having a picnic. "It's a nice place for families to spend time," said Nora Busra, a 35-year-old Singaporean mother.

This is not an ordinary park. It is located on the circular rooftop of a building, which houses Singapore's Public Utilities Board (PUB) or national water agency. Next to it, the Marina Barrage, wide as a two-road lane, keeps out the seawater from the 350-metre wide channel. It creates a 10,000 hectare freshwater lake, known as the Marina Reservoir, and provides 10 percent of the local water supply.