At the Earth's Core - (Fantasy / Science Fiction) - 1976

Dr. Abner Perry (Peter Cushing) is an English scientist who has invented a massive drill that can carry people, and dig deep into the earth. Joined by his adventure-seeking American backer, David Innes (Doug McClure), Perry takes the machine on a maiden voyage through a mountain. However it digs far deeper down into the ground than it is supposed to.
Abner and David discover a pre historic underground civilisation, of primitive humans. Who live in fear of telepathic flying monsters. David becomes intrigued by the beautiful native Dia, (Caroline Munro), and must rescue her when she is chosen, as a human sacrifice for the monsters.