The Canyons

The canyons is a huge zone made of canyons and mountains. The canyons make a spiral in the mountain ending in the center. Look at the world map to see the paths of the canyons. If you follow the canyons in the right direction, you'll reach the center of the zone where you'll find a lot of waterfalls. It's a good place to pump infinite quantities of water.
You can reach this place with an airplane easily and flight trough the canyons. Unfortunately, there is no place to land. There is a little flat zone in the center, but unless you are insanely good, it's nearly impossible to land. Better build an airport if you want to land safely here.