Subterrene

A Subterrene (Latin:Subterrina) (Russian:Подземная лодка) is a vehicle that travels underground (through solid rock/soil) much as a submarine travels underwater, either by mechanical drilling, or by melting its way forward. Subterrenes existed first in fiction as mechanical drillers, with real-world thermal designs and examples following in the second half of the 20th century.