I have a soft spot for this fantastic 1970's monster movie, which I first saw as a small boy. In short, this is a highly enjoyable "cowboys v dinosaurs" B Movie, with inventive and effective special effects for its time. A group of cowboys enter into a mythical realm of dinosaurs (and an extremely cute tiny prancing horse), and they have to battle their way out to survive. The story takes place in some undefined part of Mexico, although very little Spanish is spoken by the actors. The stop-motion animation and special F/X are by the world renowned Ray Harryhausen, which should indicate how good the creatures appear on screen (think of the scene with the skeletons in the original Jason and the Argonauts, and that will give you a good idea of the sorts of effects used in this movie). Highly imaginative, with several memorable sequences, including a fight between a cowboy and a dinosaur in a church, and an attempt to capture one of the dinosaurs with lassoes. The film builds slowly at the outset but soon works up a good pace. This is one of those movies which, like Westworld of the same era, or Barbarella from the previous decade, is crying out for a modern remake with top-notch current special effects. Somebody like Stephen Spielberg, who did of course make ET, would do a wonderful job of revamping this classic monster flick, perhaps using somebody like George Clooney in the lead role as one of the cowboys. In any case, I look forward (hopefully) to the release of Gwangi on Blu Ray, which is long overdue.