1957 Sci-Fi film "The Land Unknown" takes you on a lost-continent adventure: " A small crew led by Comman- der Harold Roberts [Jock Mahoney] and woman reporter Maggie Hathaway [Shawn Smith] are on an expedition into Antarctica for the United States Navy. During a helicopter flight ...rotor is damaged by a collision with a pterodactyl. Unable to stay in the air they start to descend, and are surprised when they end up landing well below sea-level in a warm volcanic crater. Inside, they discover a steamy tropical jungle, dinosaurs, giant carnivorous plants, and human footprints. The crew encounter many dangers and perils in the jungle in a fight for survival."
Eccentric Cinema provides fine review, detailing aspects of cinema-making average viewer may learn to appreciate:
"Much of the film's budget obviously went into the elaborate sets and special effects. These positively creak by modern standards but for the "I like Ike!" era they're fairly impressive. Except for stop-motion, every major FX technique of the day was employed to depict the monsters. The Pterodactyl, man-eating plant and aquatic Elasmosaur are animatronic puppets; a pair of monitor lizards wrestle on a diorama in the obligatory 'live-animals-used-as-dinosaurs' scene. (At least it's not that familiar footage of an iguana — floppy rubber fin glued to its hide — battling a young alligator, a sequence used in God knows how many movies.) The T-Rex is a guy in a bulky monster suit, stomping around on a well-detailed miniature 'forest primeval' set. The suit's forelegs don't function but at least the head and eyes are articulated. (I've seen much worse, believe me.) Model work is above par for the period, even if one can occasionally glimpse the wires holding up the helicopter. That the movie was shot in widescreen CinemaScope helps negate the cheap look and cramped feel typically associated with completely stage-bound productions (regardless of their actual cost or how well photographed they might be)."
"Although it can't escape the clichés and conventions of both its genre and the time it was made, The Land Unknown at least benefits from brisk pacing and good performances. Henry Brandon (The Drums of Fu Manchu, The Searchers) stands out among the cast, effective as the scientist driven to madness by years of isolation in a harsh, hostile environment. As played by athletic Jock Mahoney (Tarzan Goes To India), the Roberts character — while afflicted with the terminal blandness of so many '50s sci-fi heroes — is exactly the kind of guy you'd want in charge during a crisis. He's a quick-thinking man of action but not brashly gung ho, tempering logic with empathy and compassion. (When Miller, backed by Carmen, tries to torture Hunter into revealing the location of the wreck, Roberts pulls a gun and makes them stop. "We're not gonna dig our way out of here through human flesh," he calmly asserts.) Typical for pre-Women's Lib fare, sole female cast member Shawn Smith (It! The Terror from Beyond Space) is on hand mainly to scream and wear progressively skimpier clothing."
"Perhaps I'm being a tad generous with my Film Rating score... But anyone who appreciates '50s sci-fi, or just digs dinosaur movies in general, should have a decent time with this film. It certainly beats the hell out of similar, albeit laughable, Z-budget fare such as Lost Continent (1951) and King Dinosaur (1955). If you liked The Land That Time Forgot — made nearly 20 years later but with no appreciable improvement in special effects — you'll definitely enjoy it. (Can't abide antiquated FX? Best to pass.)"
The backstory of a movie's production can be just as interesting. Wikipedia informs: "William Reynolds [Lt. Jack Carmen] recalled the studio spent so much money on their mechanical dinosaur that they couldn't afford to shoot the film in colour as they first planned." Star Jock Mahoney holds title of oldest Tarzan in cinema history, starring in early sixties' films at age 44. Mahoney also married actress Margaret Field and was stepfather to Sally Field.