The ultimate road movie about LA's ultimate road

The guide on how to read David Lynch's Mulholland Dr comes at the start of the film. When you hear people talking, they'll call the picture Mulholland Drive. You'll see that in print, the way we refer to Billy Wilder's classic from 1950 as Sunset Boulevard. But Lynch leaves no room for doubt. The camera closes in on the street sign, one of those Los Angeleno pressed-tin jobs, that reads Mulholland Dr. And while it's not my place to remark on the film – beyond calling it a work of genius – this is a movie to be experienced as both a drive and a dream. Whether or not you can go the whole way with Mulholland Dr depends on how you feel being dr'd or dr'n.

Years ago, it was actually Sunset Blvd – and you could make a case for that film being "Sunset, Beloved". But is the fond farewell waved to Joe Gillis, to an era of Hollywood splendour, or to the movies as a whole?

What makes Los Angeles a treasury for semiologists is that nearly everything has its sign – and often the sign becomes the thing itself. What other great city is so naïve and yet so sophisticated as to have a signpost, HOLLYWOOD, in high white letters so that every aircraft coming in to LAX can see it. LAX, by the way, is not the city's purgative; just the purgatory by which you come and go.

As for Mulholland Drive, you knew it before you'd heard of it. Because everyone who has ever wanted to capture LA at night – the diamonds tossed on black velvet – is told to go up on Mulholland. You see, Mulholland Drive is not just a road, it is the crest of the line of hills that separates LA from the San Fernando Valley to the north. The road runs west from downtown (close to the HOLLYWOOD sign – and that was HOLLYWOODLAND, once, an advert for a development scheme), all the way to the Pacific, north of Malibu.

Once upon a time it was offered as a way for downtowners to go to the beach quickly. But it is not a fast road. Even in its best stretches, it twists and turns with the ridges. And these days, once you get beyond the San Diego Freeway, Mulholland is actually dirt road. That's a place for motor-bike riders, for drug-deals and worse. It's not a place where I'd recommend picking anyone up.

But in its best section, from Coldwater to Laurel Canyons, it has great mansions, or bunkers, built to permit every private indulgence and keep out every fan. Why not? Cielo Drive, a stone's throw south, is where the Manson gang came in one summer night in 1969. It's wild country with the best views in town.

There's one more meaning in the name. Mulholland was William Mulholland, director of water and power for Los Angeles in 1913. He saw ample water far to the north, in the Owens River Valle – "sierra snow" water he called it, where it was being no more than scenic or environmental. He had a genius for realising that LA might be a great city (it was small still in 1913), famous for designing dreams, if it had a water supply. So he built an aqueduct, more than 200 miles, led the water to the city and told Los Angeles, "There it is – take it". He is the model for Charles Mulwreay in the film Chinatown. That man has a conscience; he is aware of the power plays and the intrigue in water politics. He regrets what he has done. Whereas, the real Mulholland seems to have slept peacefully – except when he was dreaming.

d.thomson@independent.co.uk

'Mulholland Dr' (15) is released on 4 January, 2002