The film fits into that whole 'hell on earth' genre which was made popular by Lucio Fulci's The Beyond in 1981. The plot focuses on a bunch of cave explorers that find a gate to hell under the Earth's crust, with disastrous(ly boring) results. Seriously, this has to be one of the very worst films of its kind - there's absolutely NOTHING of interest in the whole film. Not even the special effects offer any entertainment...not that the film is particularly gory anyway. It really does just drone on for the entire torturous running time and there's absolutely no reason to bother tracking this dross down.
