Hollywood was a part of the city of Los Angeles known for its connection to the movie and entertainment industries of the 20th and 21st centuries. The "Hollywood" sign was among the Earth cultural items the Threshold stole and moved to the town of Wormwood on the Moon. The moon was later destroyed; the sign likely was also. (COMIC: Wormwood)
Visits by the Doctor
In 1921, the First Doctor, Steven Taylor and Sara Kingdom visited a Hollywood film set, though they did not know where they had landed and thought they were in an insane asylum. (TV: The Daleks' Master Plan)
In 1926, the Tenth Doctor visited Hollywood and met Archie Maplin, Emily Winter and Matthew Finnegan. He noted the city's famous "Hollywoodland" sign, commenting that he always preferred the sign before the "Land" was removed from the end of it. (COMIC: Silver Scream)
In 1961, the Thirteenth Doctor, Graham O'Brien, Ryan Sinclair and Yasmin Khan visited Paramount Studios to return Audrey Hepburn's sunglasses, where they encountered the KaaDok. (PROSE: Mission of the KaaDok)
In 2012, the Tenth Doctor and Donna Noble visited Hollywood. The star and alien Amelia Hubble. She had fed on the creative plasma energy of people in the film and television industries. This had caused production and activity in the city to diminish drastically. The Tenth Doctor convinced her to take the energy she needed from the Internet. When the Doctor and Donna returned to Hollywood a year later, everything was back to normal. (COMIC: Nightmare on the Boulevard)
Behind the scenes
Though it's possible that a real world location doesn't exist in the same geographic space in the Doctor Who universe, such cases are few and far between. Thus, the map at right is probably a good indicator of the DWU location of Hollywood.