An open pit is a hole in the earth formed by excavation, which is bounded on all sides by its own walls, and which is fully open to the atmosphere. This includes open-pit mines and quarries as well as other excavated holes. Building excavations are not listed as open pits unless construction is permanently aborted and the site is not filled in. Narrow shafts, underground mines, and tunnels are not listed as open pits. An open pit's existence as an object of this type comes to an end when it has been filled in by landfill or converted to an artificial pond.

The excavation has its own surrounding walls and is wholly open above. A narrow shaft or a roofed underground cavity has a different form.

A normal building excavation has the exclusion stated above. Filling the pit or turning it into an artificial pond ends its continued existence as an open pit.