This feature is your classic 'tunnel to the centre of the earth' scenario but on this occasion they are doing it in search of another place for people to live after they have come to the conclusion that soon the earth will not be habitable after the event of a nuclear war. A bog standard drilling machine that also houses the crew is constructed and after some external funding our hero's get on their way.
Throughout the film I felt as if it was almost a science lesson to the viewer, the way the characters explain why stalactites and caverns are formed when everyone in the group knows how they are formed because they are all seasoned scientists or at least harbour a few brain cells. The world they are exploring is not your typical centre of the earth filled with dense jungles and dinosaurs but rather just normal caverns and miles of stalactites so to stop us getting bored we see two of the main characters kicking of every five minutes with our busty companion getting in the mix to sort it out.
At one point some silly sausage leaves the ships only water exposed to some dangerous gasses and spoils it all but for some reason to the woman of the group this is the least of her worries as you can blatantly see in her chops when she discovers Rabbits can't breed in this underground world. I thought rabbits lived and bonked underground myself, I think this happened because of the vibrations from the drilling machine digging a good 1600 miles underground through solid rock that seen all the test rabbits babies of but that's just me.
It may seem pretty ridiculous in places but I'm sure this film had allot to say back in 1950, being only 5 years since Hiroshima people would have been predicting similar things about the end of the world and the ideas in such films might have frightened people more than any horror film at the time.