Mark Twain said the coldest winter he ever spent was a summer in this city. But Miles Archer was colder. Dead cold.

Some babe iced him above Stockton Street. She was a redhead named Brigid O`Shaughnessy with cobalt-blue eyes, long legs and a look that got as much attention as the barrel of a .38.

A private eye named Sam Spade got the goods on her in ''The Maltese Falcon'' and sent her up the river.

The man behind Spade was the gifted writer who created him, Samuel Dashiell Hammett. He lived here in San Francisco from 1921 to 1929 and used city locations for his novels.

None of his writings rose to more prominence than the ''Falcon,'' and its landmarks still abound for the literary tourist.

It`s also a great way to see parts of this historic city neglected by tourists who are reluctant to leave Fisherman`s Wharf, North Beach and the Golden Gate Bridge.

Hammett was a good-looking, dashing sort of tough guy, who worked as a private investigator for the Pinkerton National Detective Agency.

Tuberculosis began to slow him down and he turned to writing. Realizing that writers for pulp magazines knew nothing about detective work, he drew on his career experiences. Hammett`s several crime yarns were built on memories, not dreams, and he soon became leader of the ''hard-boiled'' school of detective fiction.

Even after half a century, the ''Falcon'' holds up very well.

Brigid O`Shaughnessy hires Spade and his partner, Miles Archer, to help her. Archer is bumped off and Spade runs into several people who, like O`Shaughnessy, are looking for a black bird. The statue of a golden falcon, encrusted with jewels, was painted black to hide its value. But its wealth was known to O`Shaughnessy, her partner Floyd Thursby, and two competitors, Joel Cairo and Casper Gutman.

The popularity of Hammett`s detective led to a radio show called ''The Adventures of Sam Spade,'' starring Howard Duff, and the ''Falcon,'' itself, was made into a movie three times.

In 1931, it starred Bebe Daniels and Ricardo Cortez. Bette Davis and Warren William did the second version in 1936, titled ''Satan Met a Lady.''

But by far the most memorable version was the 1941 version with Mary Astor and Humphrey Bogart.

For decades, movie detectives would try to copy Bogart and writers to imitate Hammett.

The first stop on the Hammett tour, a blend of reality and fiction, is Nob Hill, where mansions have been replaced by luxury hotels. Some of the steepest streets in the city are here and perfect for photographs,

particularly when a cable car is heading down.

On the edge of Nob Hill, at 891 Post St., is the four-story brick building where Hammett lived when he wrote the ''Falcon.'' It is also widely considered to be the apartment building Spade lived in for the ''Falcon.''

At one point in the book, Spade got off the Geary Street streetcar and walked ''up'' the hill to his apartment. In another section, when Spade was protecting Brigid in his place, he left her briefly to see if Wilmer Cook, the gunsel working for Gutman, was anywhere around. ''Post Street was empty when Spade issued into it.''

A two-block walk from Spade`s is where Thursby stayed before he was gunned down by Cook. Thursby had been Brigid`s partner, but she was anxious to be rid of him. Hammett only described Thursby`s place as being on ''Geary near Levenworth.''

Just south of the intersection is the Civic Center district, home for City Hall, the Civic Auditorium, the Public Library, the Opera House and the State and Federal Office Buildings. (Credit for designing the center is given to architect Daniel Burnham, who also left his mark on Chicago`s lakefront.)

Two blocks east of Thursby`s, at Geary and Taylor Streets, is the Bellevue Hotel. In the ''Falcon,'' Hammett called it the Belvedere Hotel and had Cairo stay there in the book. He was patterned after a greasy little guy Hammett, as a Pinkerton detective, pinched in Washington for writing bad checks. In the 1941 movie, Cairo was played by Peter Lorre.

The Bellevue is in the city`s downtown section, where chic shops are not very far from cheap shops.

Across the street from the Bellevue is the Clift Hotel. It was labeled the Alexandria in the ''Falcon'' and Hammett put Gutman into a suite that had ''two windows looking out over Geary Street.'' The fat man was based on a German spy Hammett tailed during World War I. Gutman`s gunboy, Cook, found his origins in a holdup man that Hammett arrested in Stockton. The newspapers tagged the robber the ''midget bandit.''

Sydney Greenstreet played Gutman and Cook was portrayed by Elisha Cook Jr., no relation.

The Clift has been a San Francisco landmark since the 1920s and well worth a tour of its rich lobby.

Sir Arthur Conan Doyle, another famous detective writer, stayed at the Clift in 1923 during a lecture tour. His most popular character, Sherlock Holmes, would have felt right at home with the city`s fog.

On the same block as the Clift sits the 1,300-seat Geary Theatre, which has housed the American Conservatory Theatre. When Spade frisked Cairo he found a ticket for an orchestra seat here at 415 Geary, in the center of the theater district.

According to Hammett researcher William Godshalk, the ''Falcon'' takes place during a five-day period in 1928. Cairo had paid to see ''The Merchant of Venice'' at the Geary and would have seen George Arliss as Shylock.

One block from the theater, on Powell Street just off Geary, is the St. Francis Hotel. Hammett dubbed it the St. Mark in the ''Falcon'' and had O`Shaughnessy stay in the luxury hotel.

Built in 1904, the St. Francis has been a favorite resting and playing place for actors, politicians and royalty. It has been modernized with a tower addition that holds the registration desk. But the red-carpeted Powell entrance, which had a circular check-in desk during the 1920s, was where Archer worked his last case.

It was also where Hammett worked one of his last cases as a detective for Pinkerton`s in the early 1920s. Hammett said he did leg work for defense lawyers in the case of Roscoe ''Fatty'' Arbuckle, a Hollywood film comic.

Arbuckle was charged with manslaughter in the death of the delicately beautiful actress Virginia Rappe, during a boozy party on Sept. 5, 1921, which ended for them in the bedroom of his suite in the St. Francis.

He was acquitted, but his career was ruined by the newspapers, which convicted him way before the trial.

The St. Francis faces Union Square, which since 1850 has been the heart of downtown. The square`s name is not linked to labor, but rather to demonstrations held in 1860 for the Union of Northern States.

Down at 870 Market St., about three blocks from Union Square, is where Hammett worked for Pinkerton`s. He quit before his 28th birthday in 1922.