Kola Superdeep Borehole is not massive. It's a small cylindrical hole in the ground: https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole#/media...
Mponeng is a massive continuously commercially operating mine with 5k workers
https://en.wikipedia.org/wiki/Lake_Baikal#Geography_and_hydr...
[...] and below this lies some 7 km (4.3 mi) of sediment, placing the rift floor some 8–11 km (5.0–6.8 mi) below the surface, the deepest continental rift on Earth.
halamadrid•2h ago
Cycl0ps•1h ago
https://www.youtube.com/watch?v=H6Ma0SVjMHA
bastawhiz•13m ago