This movie made me feel claustrophobic, but not because everything happens underground or in tight caves, but because the camera is always zoomed in super tight to hide interactions of the cast with all of the rubber-suited monsters. The Sagaths are prehistoric birds with the ability to telepathically control everyone and it's a good thing because they can't fly for shit. Some of the other beasts, like two huge boar/rhinos that had a bloody battle, were corny looking but were kind of cool.

Doug McClure (David) beats up any and everything in his path and has a particularly up close and personal battle with some sort of nearly immobile lizard thing. The "Iron Mole" drilling vehicle is extremely neat and I wished it had been featured in the movie more than it was. Peter Cushing plays a silly but smart old doctor and Caroline Munro is underused as princess of the underground.

I would advise against playing any drinking games associated with how many times David yells "Doc!!!" or the Doc yells "David!!!" You will surely die from alcohol poisoning.