The Dutch unique improvement.
- Constructed on:
- +3 Food
- +1 Production and +2 Gold after researching Economics
Thanks to the Polder, the Dutch are the only civilization able to make use of marshes. In their hands, the swampy land turns into a fertile paradise, and later is even able to aid Production and Gold income! Look for every opportunity to settle areas with marshes or flood plains to make maximum use of this ability!
There is, however, a caveat. Since marshes by themselves are undesirable, the border expansion AI seems to avoid expanding to marsh hexes, even when playing as the Netherlands. As a result, sometimes you have to spend gold to buy the marsh hexes needed to build Polders.
Polders can be built anywhere, not just in Dutch territory. If playing in an alliance with a Dutch player, it's a good idea to refrain from improving marsh and flood plains tiles until the Dutch can send a Worker to build Polders abroad.
A polder is a low-lying tract enclosed by dikes with the water drained. In general, polder is land reclaimed from a lake or seabed, from flood plains, or from marshes. In time, the drained land subsides so that all polders are eventually below the surrounding water level. Because of this, water seeps into the drained area and must be pumped out or otherwise drained. The dikes are usually made of readily available materials, earth or sand; in modern times these barriers might be covered or completely composed of concrete. The drained land is extremely fertile and makes excellent pasturage or cropland.
The first polders of reclaimed land were constructed in the 11th century AD, although building embankments as barriers to water date back to the Romans. The Dutch have a long history of reclaiming marshes and fen-land, and even the seabed, and possess half of the polder acreage in Europe. Although there are polders in other countries of Europe, and examples can be found in Asia and North America, the Netherlands have some 3,000 polders accounting for about 27 percent of the country's land. Amsterdam itself is built largely upon polder. As the Dutch homily states, "God made the world, but the Dutch made the Netherlands."