From Dwarf Fortress Wiki
A tunnel is a goblin or dwarf-made construction that connects sites together, much like a road but underground. When embarked on in fortress mode they are capped at the map edge, preventing any visitors from using them.
|World Generation (Basic/Advanced) - Regions - Climate - Surroundings - Map legend|
|Civilizations - Sites ( Cave - Town - Fortress - Ruin ) - Calendar|
|Aquifer - Brook - Island - Tunnel - Volcano - Waterfall|
|Biomes|| Chasm/Caverns - Desert - Forest - Glacier - Grassland - Lake - Mountain|
Murky pool - Ocean - River - Savanna - Shrubland - Tundra - Wetland