CREDITS THE EXORCIST, 1973 dir: William Friedkin Ellen Burstyn Jason Miller Linda Blair Max Von Sydow

Massively hyped on release, picketted by fundamentalist Christians – the kind of publicity you just canít buy – The Exorcist set new standards for gross-out horror movies.

Author William Peter Blattyís stated intention was a movie about Catholic faith. Director William Friedkin wisely dumped Blattyís flakily religiose ëThousand Points of Lightí ending, with souls twinkling in Heaven.

The opening scene, of Father Merrin (Ingmar Bergman regular Max Von Sydow) confronting the demon Pazuzu, is pre-Saddam Hussein Iraq. The location was a real archaeological dig near Al Mawsil, and the town where Father Merrin suffers is Hatra.

Movie actress Chris MacNeil (Ellen Burstyn, playing a character supposedly based on multi-reincarnated Shirley MacLaine) is making a student-protest movie on the campus of Georgetown University, Washington DC ‚ author Blattyís alma mater. Itís on campus that the Dahlgren Chapel is obscenely desecrated.

Father Karras (Jason Miller) visits his sick mother in New Yorkís Goldwater Memorial Hospital on Roosevelt Island in the East River (for a long time the site of madhouses and prisons – it was here Mae West served her eight day sentence in the 1930s for appearing in her play Sex). The hospital is a major setting for John Boorman's very different Exorcist II: The Heretic.

The aerial tramway that takes you to Roosevelt Island is featured in City Slickers and hijacked by the Green Goblin in Spider-Man.

The possessed house itself stands at 3600 Prospect Avenue at 36th Street NW, close to the Potomac River in Georgetown, southwest DC, but itís not quite as seen in the movie. You wonít be able to spot the window of Reganís room, from which the ominous shaft of light floods in the poster image. This wing of the house was no more than a false front built for the movie.

Father Karras plummets down the flight of steps leading to M Street, Georgetown, Washington DC

You can, though, find the flight of steps down which Father Karras hurtles, alongside the house, leading down from Prospect Avenue to M Street.

The complex interior set, with moving walls and refrigeration, was built at the Ceco Studios (now called Cameramart), 450 West 54th Street between 9th and 10th Avenues in New York.