In the Star Trek episode “What are Little Girls Made Of” a vast system of subterranean ruins is discovered on the planet Exo-III. As the sun of the star system is fading, surface temperatures are below -100°C and the former inhabitants constructed a vast system of underground caverns to survive beneath the frozen surface, eventually perishing anyway.
Not only aliens, also humans dig into planets in the Star Trek universe. In the episode "The Devil in the Dark" the Enterprise visits a mining colony on the planet Janus VI, or more precise, inside the planet, as the mine is a large underground facility.
People were excavating tunnels way back in the Bronze Age. An 82 ft long tunnel in Tyrol, used to mine for copper ore, has been dated to 2800 BCE. In historic times, tunnels were constructed to provide water for settlements, like Mycenae around 1200 BCE and Jerusalem around 1000 BCE. The 541 ft long Malpas-Tunnel in France, constructed in 1679-1681, was the first traffic tunnel entirely excavated with the help of gunpowder.
People were excavating tunnels way back in the Bronze Age. An 82 ft long tunnel in Tyrol, used to mine for copper ore, has been dated to 2800 BCE. In historic times, tunnels were constructed to provide water for settlements, like Mycenae around 1200 BCE and Jerusalem around 1000 BCE. The 541 ft long Malpas-Tunnel in France, constructed in 1679-1681, was the first traffic tunnel entirely excavated with the help of gunpowder.
Humans nowadays create vast tunnel systems beneath cities, rail and road tunnels beneath mountains and even seas, mines to extract ore and boreholes that penetrate deep into Earth's crust. Especially during the great acceleration during the industrial revolution humans started to excavate large cavities, being orders of magnitude greater in scale as animal burrows.
Such cavities and galleries have a high potential for long-term preservation, as they are safe from surface erosion some will be preserved for millions and even billions of year into the future.
