The best-known examples are those polders that constitute areas of land reclaimed from a body of water, such as a lake or the sea, and are consequently below the surrounding water level.

This requires drainage by pumps to prevent the water table within the polder from rising too high. Some can be drained by opening sluices at low tide.

Polders are most commonly found, though not exclusively so, in river deltas, former fenlands and coastal areas. [The Netherlands] is frequently associated with polders: 'God created the world except for the Netherlands. The Dutch took it from the sea’.

The Dutch have a long history of reclamation of marshes and fenland, not only within their country but also abroad. About half of all polderland within northwest Europe is located within the Netherlands. The first embankments in Europe were constructed in Roman times. The first polders were constructed in the 11th century. This also leads to the expression used to describe Dutch decision making - the Polder Model.