Mystery Flesh Pit National Park:

As the name suggests, it's a giant flesh tunnel opening through the Earth's epidermis, dermis, hypodermis, and more, revealing colossal esophagi and leviathan spleen. As you descend, you may encounter "spasm fits" and "gastric ejecta" or feel your bodily moisture being "leeched." Deviate from the marked trails and you risk digestion, lethal entanglement with "Macrobacteria" and "Abyssal Copepods," or a splattering of "amniotic secretions."

Feast your eyes upon it, O mortal.

D̷̺̕ȯ̸̗ ̸͈͂y̷"̚o̵͐͜ü̷͖ ̶͉͑f̷̓͜e̴̻̒ḛ̴̆l̷̩̊ ̴͕͆i̸͕̒ẗ̶̖́ ̴̤͠b̵͎̽e̵̖͛c̵̤̆k̸̦̈́ȍ̵̱n̴̟͊i̴͖̅n̴̦̐g̷͖͘?̸̼̍

Roberts describes the MFPNP as such:

The Mystery Flesh Pit is the name given to a bizarre natural geobiological feature discovered in the permian basin region of west texas in the early 1970s. The pit is characterized as an enormous subterranean organism of indeterminate size and origin embedded deep within the earth, displaying a vast array of highly unusual and often disturbing phenomena within its vast internal anatomy.

Following its initial discovery and subsequent survey exploration missions, the surface orifice of the Mystery Flesh Pit was enlarged and internal sections were slowly reinforced and developed by the Anodyne Deep Earth Mining corporation who opened the Pit as a tourist attraction in 1976. In the early 1980s, the site was absorbed into the National Park System which operated and maintained the Mystery Flesh Pit until its sudden closure in 2007.

Previously, previously, previously, previously, previously, previously, previously.