Behemoth the seamonster (1959)

aka The Giant Behemoth.
"Something has happened here that isn't in the book."
Radioactive waste dumped at sea brings back a dinosaur with a desire to visit London, but the would be tourist isn't welcome, probably because he seems intent on wrecking the place.
Good b-movie creature feature, as long as you revel in its low budget.

the beast from 20,000 fathoms (1953)

"You know every time one of those things goes off, I feel as if I was helping to write the first chapter of a new Genesis."
The army decide to conduct a nuclear test in the arctic. Unfortunately this thaws out a huge dinosaur which for want of anything better to do decides to head for New York. Its up to Professor Tom Nesbitt (Paul Hubschmid) to stop the destructive beast.
Entertaining creature feature making great use of Ray Harryhausen's unique talents to bring the monster to life.

the colossus of new york (1958)

"...your father has just become a famous man."
Dr Jeremy Spensser (John Baragrey), a genius and humanitarian, dies in an accident. His father (Otto Kruger) being a brain surgeon, decides to save his brain and places it within a robot body. But not just any old body, one that is 12 feet tall and possessed of enormous strength! Initially things go well, until the robot reveals it has developed ESP and predicts a number of catastrophic accidents and wants to go out into the world, but is prevented by his father and brother. What lengths will the robot go to to end its seclusion?
An interesting take on the Frankenstein story, with the mind of a gentle genius being warped by its seclusion and deprevation. Entertaining, but talky sci-fi.

gorgo (1961)

After an earthquake disrupts a small fishing village in the West of Ireland, a salvage ship captures a large dinosaur like creature. A circus owner pays them to display it in London and names it Gorgo. But what they don't know is that Gorgo is in fact a youngster and his mother wants him back.
An unasshamed rip off of Godzilla, a bit of King Kong and some Beast From 20,000 Fathoms, but adds the twist of a mother's love and her distruction of just about every bit of London a tourist will know of: from the houses of parliament to Piccadilly Circus, they all get stomped. A surprisingly good cast, including Bill Travers and William Sylvester, get to run around as a child spouts portents of doom at them. Not up to the mark of the original Godzilla, but still an enjoyable twist to the genre.