meet you a mile underground...
Well not really a mile but a hundred feet perhaps? This is the "Rotunda" in Mammoth Caves National park in Kentucky, right here in the USA.
The park was established as a national park on July 1, 1941. It became a World Heritage Site on October 27, 1981, and an international Biosphere Reserve on September 26, 1990.
It is centered around the Green River, with a tributary, the Nolin River, feeding into the Green just inside the park. With a confirmed 365 miles of passageways it is by far the world's longest known cave system, being well over twice as long as the second longest cave system, which is South Dakota's Jewel Cave with 145 miles of passageways.