Waterfall

From DwarfFortressWiki

Waterfalls can be found often in mountains. To locate them in the region map, check for rivers that cross tall cliffs.

Waterfalls, like any other falling water, generate mist that makes your dwarves happier: "He was comforted by a lovely waterfall lately." (Mist makes dwarves happy even if it's just from water cascading down a stairway, which in real life might be more a cause for alarm.)

Waterfalls can be used to drive water through a fort with nothing but gravity power: just push it through whatever channels you desire and off the cliff side when it's done its course. Large reservoirs could probably be created by building a dam at one end.

If it's cold enough for water to freeze, the waterfall will freeze as well, forming a partial wall.

Overworld
World generation - Regions - Biomes - Civilizations - Map legend - Sites - Armies
Aquifer - Brook - Cave - Chasm - Forest - Lake - Mountain - Ocean - Pit - River - Volcano - Waterfall