Subway tunnels snake beneath city streets—some just 20 feet down, others nearly 200 feet below. In New York, for example, 191st Street Station plunges an incredible 180 feet underground, deep into the bedrock.

But before a single tunnel is dug, engineers meticulously map out everything hidden beneath the surface: subway lines, sewers, gas mains, electrical conduits—even the forgotten infrastructure of older cities. It’s a 3D puzzle made of concrete, steel, and risk.

To thread new tunnels through this maze—or build skyscrapers above it—engineers drive massive steel and concrete supports deep into the earth, anchoring them in the bedrock below. Some buildings stand on hollow ground, balanced on foundations that bypass tunnels entirely.

It’s not just construction. It’s precision choreography—beneath your feet.