He sinkholed his lair, which means -(mechanical whirring) -he's gone back underground.
He'll stay underground the rest of his life.
Also underground, tram and main rail within a couple of minutes walk.
All right, I'll need Metro at the train stations and underground.
The number of miners employed underground fell by approximately 10000 between the beginning and end of 198I.
Furthermore, underground working conditions raise the need for specific improvements with regard to occupational health and safety.
