Kansas city SubTropolis

The underground tunnels of SubTropolis have been around much longer than the companies housed inside of them. During the 1940’s, miners started work on a 270-million-year-old limestone deposit, called Bethany Falls. This process resulted the 55 million square-feet mined out of the Bethany Falls layer, with 14 million square-feet usable for underground industrial space. The miners then recycled the deposits. These deposits eventually helped to create the tarmacs at the Kansas City airport, and were used to pave Interstate 435.


In the 1960’s, Hunt Midwest realized there was an opportunity for business expansion, not on the surface, but below ground. With the heavy-lifting done 20 years prior, they determined construction would be less expensive underground than a normal industrial building would be on the surface. The mining process also left 25-foot square pillars on 65-foot centers and 40 feet apart––which turned out to be ideal for planning square footage of new office space.


Dug into the Bethany Falls limestone mine, SubTropolis is, in places, 160 feet (49 m) beneath the surface. It has a grid of 16 ft (4.9 m) high, 40 ft (12 m) wide tunnels separated by 25 ft (7.6 m) square limestone pillars created by the room and pillar method of hard rock mining. The complex contains almost 7 miles (11 km) of illuminated, paved roads and several miles of railroad track. Currently, more than 6,000,000 square feet (560,000 m2) is occupied and 8,000,000 square feet (740,000 m2) are available for future expansion.


KD: Wondering whether they really excavated all that in the 1940s, or merely cleared an older cave system.
  • In the video they say that pillars are 3 times stronger than concrete. What material are those pillars made of?
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