The “Main Cave” portion of Mammoth Cave is the large level B passage that starts at the Gothic Avenue intersection, extends to the southeast & south, and ends at Violet City, very near a surface sinkhole.
The only current, regular cave tour that allows examination of the entire stretch of the Main Cave is the “Violet City tour”, which is conducted using hand-held lanterns. The stretch from Gothic Avenue to Giant's Coffin can be seen on the “Historic tour” and the “River Styx tour”. The “Star Chamber tour” includes a walk in the Main Cave from Gothic Avenue to Star Chamber, just beyond the tuberculosis cottages.
An interesting illusion was discovered during early cave tours of the Main Cave. It can be witnessed between the intersection with Gothic Avenue and the large breakdown block called Giant's Coffin. When the Main Cave-Gothic Avenue intersection is illuminated, the sinuosity of the Main Cave's passage, as seen from the east, creates an irregularly tapering pillar of light. Early visitors perceived a likeness to Martha Washington, America's first First Lady.
Martha Washington's Statue (from Hovey & Call, 1912; original photograph by Benjamin Hains). Looking in the old downstream direction of the Main Cave (looking WNW).
The very large breakdown block called “Giant's Coffin” is a regular stop on many Mammoth Cave tours. It consists of upper Ste. Genevieve Limestone (upper Middle Mississippian). Some graffiti is present on Giant's Coffin (& throughout this portion of Mammoth Cave).
Giant's Coffin (looking ~SW) - large breakdown block in Mammoth Cave's “Main Cave”.
Giant's Coffin (looking ~WNW) - the Historic & River Styx cave tours walk through the Main Cave as far as here, then head down to lower levels (levels C, D, E, and F). A narrow passage (“Dante's Gateway”) exists behind this large rock (see below), just around the corner on the left in this picture.
Giant's Coffin (looking ~NNW) (from an old postcard; original photograph by Nat Wigginton) - Dante's Gateway is the opening on the left side of the Giant's Coffin breakdown block.
Giant's Coffin (southeastern corner of block) - Dr. Joseph Nash McDowell's 1839 scratch signature is the most well-known piece of defacement on Giant's Coffin. McDowell was a famous 1800s physician and surgeon in Midwestern America, despite his eccentric, outrageous, foul-mouthed, insulting, gun-loving, and grave-robbing nature. McDowell had been aware that tuberculosis (TB) patients were experiencing improved symptoms after having spent time in Alpine settings in Europe. He suggested that cool, subterranean air might have the same effect. This thinking resulted in a TB curative experiment in Mammoth Cave in the 1840s.
To the south of the Giant's Coffin breakdown block is a noticeably sharp left turn in the trend of the Main Cave. It is a prominent landmark called the Acute Angle (aka Great Bend). The passage of the ancient underground river suddenly turns at about a 60 to 70 degree angle.
Acute Angle (from Hovey & Call, 1912; original photograph by Benjamin Hains) - looking ~SE.
Between the Acute Angle and the Star Chamber are the remnants of an early 1840s experiment in curing tuberculosis (TB; formerly called consumption). TB patients in Europe perceived improvements in their symptoms while hanging out in cool, high Alpine settings or in cool cave settings. Two cottages were set up in the Main Cave and TB patients were invited to live in this stretch of the cave. The consumptives’ symptoms did not improve. Deaths occurred and the experiment ended after 10 months.
Tuberculosis cottage (from an old postcard)
The Star Chamber is located in the Main Cave just beyond the tuberculosis cottages. This is absolutely my favourite part of Mammoth Cave (but I've not had access to any features beyond the modern, regular tourist trails). The walls are principally limestones of the upper Ste. Genevieve Limestone (Levais Member & Aux Vases Member).
Star Chamber gets its name from the presence on the ceiling of numerous spots of whitish material with a black background. If you lie down on your back on the benches, an amazing & moving illusion appears. One experiences the feeling of being in a rock-walled canyon with just stars & space above. I'm sure the illusion is much more moving in a quiet setting. Incessant talk by NPS rangers & other people on the tour don't allow for this, of course. However, I've never been so drawn to any one spot in any other cave.
A large, somewhat rounded whitish area on the ceiling is often referred to as the Moon. A line of whitish material near “the Moon” is said to represent a comet or a meteor. Neither of these features is apparent in the photo shown below.
Star Chamber (from an old postcard) - explanations accounting for the origin of the Star Chamber's ceiling vary. First of all, it is not a natural feature. That doesn't ruin the awesomeness of it for me, however. The ceiling in the Main Cave is, in many areas, coated with a crust of gypsum (CaSO4·2H2O). The original, natural color of the gypsum ceiling crust was white. It is now black in color from centuries of torch smoke from prehistoric Indians and countless cave tours.
The “stars” have been explained by some as being spots where new ceiling crystals have grown downward, pushing away the black crust. That phenomenon has occurred in Mammoth Cave, and likely occurred here. But I'm pretty sure that's not the origin of many of the stars in the Star Chamber.
OK - look at the stars in the above photo. Note that they are not randomly distributed on the black ceiling. They're concentrated near the center. There are few to no stars near the ceiling-wall intersections. It would be expected that new ceiling crystal growth pushing away old black gypsum crust results in a randomly distributed “star field”.
It is known that during some early cave tours, guides and visitors threw rocks at the ceiling here to create new stars. The rock impacts knocked away blackened gypsum crusts. The pale color seen at each star is either whitish gypsum or whitish limestone.
During the 1930s, in the southeastern stretches of the Main Cave, cave guides discovered the desiccated corpse of an American Indian that had been crushed under a limestone block. It had been known that prehistoric Indians entered & used Mammoth Cave - the oldest known evidence dates to about 2170 B.C. Indian artifacts have been found as far as 12 miles in. Their known activities included the collection of gypsum crystals from the walls of the historic section of Mamoth Cave.
In the case of this Indian mummy, nicknamed “Lost John”, he had been digging for gypsum under a moderately heavy piece of limestone breakdown. The block of rock shifted and trapped him. Examination of the corpse while under the rock revealed that he had time to get his head and arm out from under the rock, but not the rest of him. Autopsy of the corpse provided some diet information - hickory nuts and sunflower seeds were in his stomach. Intestinal tissue from this mummy has been isotopically dated to about 15 B.C. Cloth associated with the body has been dated to about 445 B.C.
The original limestone block is still viewable on the “Violet City tour”. It's along the eastern side of the Main Cave, on a slab-covered ledge. It has some metal straps wrapped around it, which were used in lifting the rock during recovery of the mummy.
Indian Mummy (from an old postcard) - “Lost John” was on long-term public display at the discovery site & then at Giant's Coffin. A couple other mummies found much nearer to the mouth of the cave were discovered in the 1800s and reburied somewhere in Houchins Narrows. Indian mummies from other Kentucky caves were sometimes put on display at Mammoth Cave, including near the entrance to Gothic Avenue (see photo below). Stories about these mummies usually gave the incorrect impression that they, too, were found in Mammoth Cave. Most of them were not found here.
Sadly, this interesting part of Mammoth Cave history is now inaccessible. The mummy was reburied in the 1970s in a spot near the discovery site. The exact site is known only to the Mammoth Cave superintendent (& a few other people). I detest censorship of visual information. So, I present the old postcard photo shown above so that everyone can better appreciate a small, but fascinating, part of American history.
“Mammoth Cave Mummy” (from Hovey & Call, 1912) - this specimen was discovered in nearby Salts Cave back in the 1800s. It was put on long-term public display near the mouth of Gothic Avenue (in the “Mummy's Niche”). It eventually ended up at the United States National Museum (USNM; aka the Smithsonian Museum) in Washington D.C. Published isotopic dates on this mummy range from about 10 B.C. to A.D. 130.
Enormous piles of breakdown occur in places in the Main Cave. The piles of large rocks reminded early visitors of the flood-ravaged ruins of ancient cities. Each major breakdown pile was thus called a “City” (“First City”, “Second City”, etc.). Those early names are retained for two of the largest breakdown piles in the Main Cave - Chief City and Violet City. Chief City is the larger of the two rock piles. Violet City is a rock pile at the southernmost end of the Main Cave, which is directly below a surface sinkhole. Downward percolating water from the sinkhole has resulted in some nice speleothem in the upper parts of the Violet City breakdown pile (see below).
Violet City (from an old postcard) - nice travertine speleothem covering a portion of the Violet City breakdown pile (loose rocks visible at bottom of photo). The speleothem consists of dripstone (stalactites, stalagmites, columns) and flowstone. The surface sinkhole is uphill to the left. Violet City is the southernmost and upstream-most portion of Mammoth Cave's Main Cave.
Violet City (from an old postcard) - dripstone & flowstone covering part of the upper Violet City breakdown pile.