Cave

From Dwarf Fortress Wiki

A cave is a natural formation that occurs in mountainous or rocky areas. Some caves may contain hostile creatures or water, and vary in size from a few tiles to long, winding passageways. Caves can span many z-levels up and down.

Caves tend to be somewhat rare when placing a fortress, the best way to find them is to take quests, ask about the surroundings, and scout for them in adventure mode. This will place them on your map, and also on the embark map for fortress mode making it much easier to build on them.

Circular caves

A circular cave in it's early stages of filling with water (a few days after embark) and some critters in it.

A circular cave at a later stage of evaporating water.

Upper z-level of a circular cave showing a connection to the outside world.

In some cases it's not rare to see a big circular cave on the map. Most of the time it's connected to the outside world and fill with water that later evaporates and leaves farmable soil or a tower-cap farm. It is not sure if this kind of a cave is shown on the embark screen.^Verify