20 Million Miles to Earth (1957) starring William Hopper, Joan Taylor

In 20 Million Miles to Earth, the first human expedition to Venus returns to Earth with a bang – literally. The ship crash lands off the coast of Italy. There are only two survivors, one of whom dies shortly after. But in addition, there’s a living specimen brought back. And it begins growing in Earth’s atmosphere. It’s only dangerous when provoked. But it gets provoked easily. And after it’s being held incapacitated in the Coliseum of Rome … It escapes! That poor elephant …