Ancient underground cities and tunnels

Underground cities and tunnels from China to South America inspire as much awe today as the pyramids or Stonehenge. Where did these vast networks of corridors carved into rock thousands of years ago come from, given that ancient technology shouldn’t have allowed such feats? Some see them as shelters from wars and cataclysms, others as temples of forgotten cults or laboratories of a lost civilization that went underground to survive a global flood. There’s growing talk of their role in the Earth’s energy grid connecting the so-called ley lines, and even of contact with extraterrestrials. Could these tunnels be evidence that our history is completely different from what we were taught?