The company also shot at Hoover Dam and at the Pentagon , the first time since the September 11 attacks that film crews had been allowed at these locations . The external Hoover Dam scenes were shot before tourists arrived daily at 10:00 a.m. , with shooting moving inside for the remainder of the day . Production in California was based at Hughes Aircraft at Playa Vista , where the hangar in which Megatron is imprisoned was built . Six weekends were spent in Los Angeles , California shooting the climactic battle , with some elements being shot on the Universal Studios backlot and at Detroit 's Michigan Central Station . The crew was allowed to shoot at Griffith Observatory , which was still closed for renovations begun in 2002 and would reopen in November 2006 . Filming wrapped on October 4 , 2006
September 11 attacks
September 11 attacks
Transformers (film)