Rugged David Innes (solid Doug McClure) and doddery Dr. Abner Perry (a delightfully dotty Peter Cushing) drill their way into the earth's core in their spiffy mole machine. The duo discover an ancient prehistoric world populated by dangerous gigantic beasts and human beings who are used as both food and slaves by evil telepathic pterodactyl men. Director Kevin Conner, working from a blithely silly script by Milton Subotsky, maintains a constant brisk pace throughout and treats the exceptionally foolish premise with astonishing seriousness, thereby giving this picture a certain clunkily earnest quality that's amusing and endearing in equal measure. The lovably hokey (not so) special effects are quite (unintentionally) funny. The cheesy array of cut-price creatures in particular are positively sidesplitting: cruddy guys-in-obvious-shoddy-rubber-suits pterodactyl men, equally rinky-dink savage ape-man brutes, and a hilariously ludicrous fire-belching frog thing who blows up real good. One gut-busting highlight occurs when McClure mixes it up with a fat and clumsy giant reptile. Another priceless scene depicts a dinosaur clutching a doll in its slavering jaws. Moreover, we also get some rousing rough'n'ready fisticuffs and an exciting climactic slave revolt. It's a total treat to see Cushing gleefully ham it up in a rare broad comedic part and become an unlikely, but enthusiastic arrow-slinging action hero in the last third of the flick. The ever-luscious Caroline Munro looks positively yummy as the fetching Princess Dia, plus there are nice supporting turns by Cy Grant as gallant warrior Ra and Sean Lynch as treacherous coward Hoojah. Mike Vickers' neatly varied score alternates between jaunty orchestral music and wonky droning synthesizer stuff. Alan Hume's crisp cinematography adds a glossy sheen to the infectiously inane proceedings. A complete campy riot.