When Carl Laemmle first opened his studio in Hollywood, it was located on a former chicken ranch. During the lean early years, he invited guests onto the lot to watch the films being made, for the cost of a dozen eggs. (He was still operating the egg farm.) The studio didn't need to worry about noise; these were silent pictures. The studio was closed to outside guests when sound arrived, since they needed absolute silence during filming.
With the arrival of DISNEYLAND in nearby Anaheim, tourism flourished and Universal Studios sought to capitalize on the hordes of tourists descending on Southern California. They still needed absolute silence during production and had to restrict access to the backlot itself, so they built a fleet of "glamour trams" to escort guests around the studio's massive lot.
Since filming wasn't always going on, the studio decided to put attractions along the tram route to entertain guests. These attractions were designed to show guests how films were made. One of the first attractions placed alongside the tram route was "Rockslide".
The trams would pull alongside a hill with precarious looking rocks stationed upon it. As the tour guide discussed the impossibility of those rocks rolling down the hill to crush the tram, the hillside began rumbling and the impossible became possible. Of course, the tram would drive off, narrowly escaping sure tragedy.
