... there's a strange vibration. Nigel Williamson revisits San Francisco
On 14 January, 1967, more than 20,000 hippies gathered in San Francisco's Golden Gate Park for the first "human be-in". The event marked the beginning of the summer of love, a date which now ranks in local history with the 1849 gold rush and the 1906 earthquake. The city is now preparing to celebrate the 30th anniversary of that extraordinary year of psychedelic drugs and music.

Visitors arriving at San Francisco airport are met by an exhibition of images of Jerry Garcia, Janis Joplin and other icons of the flower power era. Every guidebook to the city contains a eulogy to "the spirit of '67" and a trip to the Haight-Ashbury district is high (pun intended) on any tourist trail. A few sad and notable casualties apart, it seems that old hippies never die; they simply become tourist attractions.

It's a far cry from the scene 30 years ago. The official police report on the "human be-in" complained of "hippies high on LSD obstructing and creating a nuisance". Dozens were bundled away in paddy wagons while the Grateful Dead, Quicksilver Messenger Service and Jefferson Airplane played for free and Timothy Leary, the LSD guru, chanted "turn on, tune in, drop out". Over the coming months, to the consternation of the city authorities, an estimated 200,000 young people heeded the call and moved into the area around Haight and Ashbury Streets, a short stroll from Golden Gate Park. Hashbury, as it inevitably was known, became the hippie capital of the world.

Some were drawn by the drugs and the "free love"; others had an interest in Eastern mysticism. But above all they were drawn by the music. In addition to the Dead, the Airplane and Quicksilver there were Country Joe and the Fish, the Steve Miller Band, Santana and Janis Joplin, all living, playing and getting high within a few blocks of each other. It was an extraordinary flowering of musical talent.

Today the sites associated with flower power's brief blooming have become much visited. Fiftysomethings who look as if they took one trip too many, and kids who weren't even born in 1967, mingle in Golden Gate Park, strumming guitars and smoking dope. There are more ponytails than at a gymkhana and sufficient acres of swirling tie-dye to induce a permanent migraine.

Top of any psychedelic heritage tour is 710 Ashbury, a large, rambling house where the Grateful Dead lived in communal style throughout 1967. It was famously busted for drugs at the end of that summer in a police raid that marked the beginning of the end of the hippie dream. The Dead moved out in March the following year. A sign put up by the owners asks the legion of "Dead heads" not to ring the doorbell. Those wishing to pay tribute to the late Jerry Garcia are invited to leave flowers: "If you do respect Jerry and believe in peace and love then you will respect our wishes and good karma will follow you in your life."

On the corner of Haight and Cole Street, a two-minute walk from the Dead's house, was the Straight Theater. As a farewell to the area, the Dead parked two flatbed trucks across the street, ran a cable from inside and played the free concert pictured on their Live Dead album. The theatre was chaotically run as a hippie community centre and didn't have a dance licence, so the bands playing there had to pretend to be giving dancing lessons. Santana were among those who got their start here. Today a "thrift store" (charity shop) stands on the site.

At the other end of Cole Street is the Panhandle, a thin, green artery running parallel to the Haight and leading into Golden Gate Park. Here the Diggers, a group of anarcho-syndicalists, dispensed free meals to hungry hippies, and it was also here in June 1967 that Jimi Hendrix made a legendary impromptu appearance with equipment borrowed from the Jefferson Airplane.

Almost every street around the Haight has tales to tell of rock'n'roll craziness.

At 112 Lyon Street, Janis Joplin lived with Country Joe McDonald. Unsurprisingly, her rowdy lifestyle did not endear her to the neighbours and Janis was evicted early in 1968. Yet it was not sex, drugs or even loud music that were her downfall here: Joplin was thrown out for a breach of the "no pets" clause in her lease. Today a sign in the house next door tells those who come to gape at the scene of her excesses, "RAD". On closer inspection it stands not for Remember the Acid Dream, but for Residents Against Drugs.

An infamous palace of rock and roll debauchery was the Jefferson Airplane's mansion at 2400 Fulton Street. The Airplane were always the aristocrats of San Francisco rock, with a big record company advance which they invested in an imposing four-storey house with Doric columns. The opera singer Caruso sheltered in the house during the 1906 earthquake, but in the Airplane's heyday the mansion rocked with infamous parties, often lasting days at a time. One celebrated bash is pictured on the front of the band's album Bless Its Pointed Little Head, with bassist Jack Casady passed out with his hand still gripped around a bottle.

With views over both Golden Gate Park and the ocean, the mansion occupies one of the prime real estate sites in the city, and the Airplane who once sung "up the revolution" eventually made a very capitalist profit on the property.

Another much-visited location is the imposing mansion overlooking Buena Vista Park where the Steve Miller Band made their early recordings in a basement studio, before the singer went on to stardom as the Space Cowboy, the Gangster of Love and The Joker. The house was later owned by ex-Hollie Graham Nash. It is much photographed by fans who believe, wrongly, that it is the home he sang about so smugly in Our House "with two cats in the yard", with Crosby, Stills and Young.

If Golden Gate Park was the birthplace of the summer of love, then Buena Vista Park at the other end of the Haight was its final resting place. The dream was too good to last and by October 1967 hard drugs and street crime were rife in the area. The Diggers organised a mock funeral in the park, at which they buried the sign from the Psychedelic Shop at 1535 Haight Street, the world's first such emporium, where half of the space was given over to a meditation room called the "calm center".

Where the Haight hippies once burnt their incense and contemplated the nature of the cosmos, you can today buy a take-away pizza.

By 1968 most of the musicians had moved out of the Haight, many of them the short distance across Golden Gate Bridge to the clean air and giant redwoods of Marin County. Just over the bridge is the harbour of Sausalito, the original setting of Otis Redding's classic "Sittin' On The Dock Of The Bay". The soul singer had become a hippie hero following his storming appearance at the Monterey pop festival and in August 1967 was playing a week-long residency in San Francisco. When his downtown hotel was besieged by female fans he was invited to stay on one of the ramshackle houseboats in the dock and the result was his best - and last - song. He died in a plane crash three months later.

San Francisco has always been a city rich in musical association. Al Jolson died here after recording a radio show with Bing Crosby, and Billie Holiday was busted for possession of narcotics. The suite where she was raided at the Mark Twain Hotel now commands a premium rate and is decorated with press cuttings of her arrest.

Fittingly, the birthplace of flower power also hosted the death of punk when the Sex Pistols split up in the city after an epic fight between Johnny Rotten, Sid Vicious and manager Malcolm McLaren at the Miyako Hotel.

Yet, musically, it will always be the summer of love for which San Francisco is best remembered. Anyone who was ever briefly touched with the spirit of 1967 will find Haight-Ashbury an evocative trip down memory lane. Get out the tie dye and the bell-bottoms, wipe the dust off those scratchy old records - and be sure to wear some flowers in your hair.

If you're going to San Francisco ...

Go now. Nigel Williamson flew just before the latest fares cut, with TWA via St Louis for pounds 346 return; he stayed at the Californian Hotel (001 415 885 2500) in the city centre for $89 (pounds 53) per night. Now, you can fly non-stop from London Heathrow to San Francisco on British Airways (0345 222111), United (0181-990 9900) or Virgin Atlantic (01293 747747). The latter has a "MegaSaver" fare of pounds 307 return, including tax, if you book before 25 January.