The gecko-shaped body of water featured in this Envisat image was formed by the Bratsk Reservoir in southeastern Siberia, Russia.
Stretching along the Angara, Oka and Iya rivers for more than 1000 km across the Irkutsk region, it is described as being 'river-like'.
The reservoir was formed in the 1960s by damming the Angara River to provide hydroelectric power. The dam, 125 m high and 4417 m wide, was built near the city of Bratsk (white area in the upper left).
Dams store water in reservoirs, from which water flows through pipes past electricity-generating turbines. The Bratsk Dam, the second of four power stations on the Angara River, has a capacity of 4500 megawatts.
Agricultural crops can be seen along the southwestern side of the reservoir, including grains, potatoes and vegetables.
This image was created by combining three Envisat radar passes (29 May, 3 July and 16 October) over the same area. The colours result from changes in the surface between acquisitions.