locomotive depot; engine shed
A railway facility where locomotives are housed, maintained, and prepared for service. Common in railway contexts.
There is a large locomotive depot in that town, where many steam locomotives are kept.
The depot staff inspected the locomotives throughout the night.
機関庫 is an older term for a locomotive shed or roundhouse, often referring to the building itself rather than the entire depot facility.
Compound of 機関 (locomotive, engine) and 区 (district, section), referring to a designated area for locomotives.