Manmade or natural: Which kind is the world’s deepest underground structure?

Underground structures can be incredibly challenging to build; however, with the proper engineering, they would prove to you that, sometimes, amazing architecture can be right at your feet.

In this video by the YouTube channel MetaBallStudies, you can see an intriguing, but rather cleithrophobic, 3D animation that compares the depth of several underground constructions. These include both human-made structures such as oil wells, laboratories, and swimming pools, as well as natural structures like caves and catacombs, among many other things.

While it should be noted that depth is measured from the lowest point to the surface, not to sea level, these cities and tunnels are represented on a real scale and will surely blow your mind. If you're curious to embark on a below-ground venture, make sure you watch the video embedded above, and as always, enjoy.