Bronson Canyon (especially the tunnel/cave) has appeared in so many movies and TV shows, it should have its own star on Hollywood Blvd. Here's a couple of frame grabs from two more 1950s sci-fi movies:
It Conquered The World
[source: RCA Columbia Home Video]
Invasion of the Body Snatchers
[source: Republic Pictures dvd]
KTLA used to air
Invasion of the Body Snatchers fairly frequently, and for a period of time in the 1970s every time it aired some local prankster would sneak around Echo Park Lake late at night leaving home-made alien seed pods. Anyone else remember that?