The Sutro Tunnel is a drainage tunnel (adit) connected to the Comstock Lode in Northern Nevada. It begins at Dayton, Nevada, and connects 3.88 miles (6.24 km) Northwest to the Savage mine in Virginia City, Nevada. The Sutro Tunnel pioneered the excavation of large drainage and access tunnels in the US. Later US mine drainage tunnels included the Argo Tunnel at Idaho Springs, Colorado, the Leadville and Yak tunnels at Leadville, Colorado, and the Roosevelt tunnel in the Cripple Creek district, Colorado.

An adit or stulm is a horizontal or nearly horizontal passage to an underground mine. Miners can use adits for access, drainage, ventilation, and extracting minerals at the lowest convenient level. Adits are also used to explore for mineral veins. Although most strongly associated with mining, the term adit is sometimes also used in the context of underground excavation for non-mining purposes; for example, to refer to smaller underground passageways excavated for underground metro systems, to provide pedestrian access to stations, and for access required during construction.