Though carved into mountainsides, dwarven fortresses and kingdoms are generally close enough to the surface that they are rarely considered to be part of the Underdark. Some dwarven mines, however, can cut deep into the Upperdark, though rarely into the Middledark unless they accidentally puncture into a pre-existing excavation.
Within their kingdoms, dwarves have created their own subterranean railroad. In addition to smaller tracks used with pushcarts in the mines, dwarves have also created tracks within their kingdoms on which larger handcars run.
Smaller cars can be operated by a single driver who pumps a lever up and down. These cars can accommodate a driver, one passenger, and a small amount of baggage or cargo. Larger handcars are equipped with a beam on a pivot that two operators stand on opposite sides of to see-saw back and forth in order to move the wheels. These handcars can accommodate the two operators plus up to six passengers and the gear they carry. Steeds the size of a horse take up the room of two passengers.
Small handcars can move at 3 miles per hour, averaging 72 miles per day if the operator and passenger trade off and continue all day and night. Larger handcars can move at 5 miles per hour, averaging 120 miles per day for continuous travel if operators and passengers trade off.
Although these tracks primarily run within a single dwarven kingdom, some dwarves have constructed railroads to travel between multiple dwarven kingdoms without exiting to the surface. These tracks primarily run through the Upperdark. Longer routes that aren’t guarded properly are often targeted by bandits and Underdark marauders seeking to rob passengers – or eat them.