Black Mountain is weirdly beautiful in and of itself, though. Back in the sixties when I was living nearby and nobody was fussed about national parks, I sat with the mountain for awhile, and poked about in the caves a bit, doing my usual thing of observing plants and rocks. It does look like a natural formation to me and I don't credit the tales of aliens, but weird it certainly is, and the pythons are formidable. Lots of interesting lichens on the open parts of the rocks, but curiously few near the cave mouths, which leads me to think that maybe some of the odd odours are sulphur-containing gases seeping up through the rocks from volcanic vents way down in the caves. Lichens don't like most sulphur compounds, and tend to die or not grow at all where such are common, which is why they are an indicator group for pollutants in cities. Such gases may also account for the suffocating sensations, stupefaction or outright hallucinations many people experience there.
Lots of flying foxes and many other bats, which can themselves generate odd gases and odours, especially from guano heaps. The disappearances may in part be due to people affected by the fumes becoming clumsy or careless in the caves, which are somewhat unforgiving. The jumbled terrain continues underground, with abrupt falls, slippery smooth or sharp jagged rocks, and enough gas to damp a candle flame. I never met any explosive gases there, but would not consider them impossible. There are local stories of relict megafauna, but I never saw any. Lots of landspirits though, not all of them friendly.
OwlsGo: are you thinking of Chinaman John's Hole at Lilyvale in Queensland? Or Hanging Rock in Victoria? That one had some girls disappear there once, probably into the caves, which were also a bushranger redoubt. Had a few experiences there myself.
