The forbidding iron portal with its creepy peephole has been replaced by an approachable glass door. The overgrown garden has been replanted, and everywhere there are coats of fresh paint.

But the Leon Trotsky House and Museum, one of Mexico City's lesser-known landmarks, is still pervasively haunted by an aura of mystery.

Half a century has passed since Trotsky, the co-architect of the Russian Revolution, commander of the Red Army and one of the 20th century's most controversial and colorful political figures, was struck down in this house. But the saffron-colored dwelling in the quiet residential neighborhood of Coyoacan still unmistakenly retains the presence and charisma of Lev Davidovich Bronstein, better known to the world as Leon Trotsky.

The blue-uniformed Mexican policeman regarded me closely as I halted on the entry path to note my first impressions of the curiously hybrid building. Once a rambling suburban villa, it was converted for Trotsky in the late 1930s to a bristling fortress with barricaded entrances and red-bricked gun turrets atop the walls.

In the center of the garden, on a white rectangular stone surrounded by cactus plants, Trotsky's name is inscribed above a huge sculpted hammer and sickle. From a flagpole behind the monument, a red banner flutters. Beneath the stone lie the ashes of Trotsky and his wife, Natalia Sedova, who died 21 years after he did.

The garden, crowded with lilies, roses, irises, hydrangeas and cacti, is enclosed by high brick and granite walls, testifying to the threat to Trotsky's life continually posed by the agents of his enemy, Joseph Stalin. Inside the parapets of what Trotsky so often referred to as "the jail," the exile spent much of his time within the restricted confines of this garden, strolling with his wife and caring for his similarly "caged" pet rabbits.

To the left of the house, a two-story green dwelling stands apart. Here Trotsky's guards and secretaries, most of whom were American volunteers, were quartered. Now the building exhibits a rare collection of photographs of Trotsky's life and the historic times he lived in.

A narrow flagstone path through the garden leads past fig and pine trees into Natalia Sedova's studio in the main house. The walls are lined with hundreds of books, mainly on art and literature. The cultured, self-effacing woman had spent 38 years with Trotsky, through all the vicissitudes of his revolutionary struggles: imprisonments, rise to power in the top Soviet leadership, political downfall and exile. After Trotsky's death, she lived on in the house for two decades, together with his only other survivor, his grandson Seva.

Next to Natalia's studio is the simply furnished, almost austere, dining room with its original furniture. A vase of fresh flowers adorns the long pinewood table; painted chairs lean against the bare walls. Above the door leading to the kitchen is a shocking sight: an ugly spray of bullet holes, made during a dawn attack on the Trotskys on May 24, 1940 -- an attack they miraculously survived.

Trotsky's personality is most vividly felt in the study. The room is almost exactly as it was in his lifetime. Dominating the high-ceilinged, whitewashed room with its original pink tint is his massive work table, its desk calendar frozen at the date of his assassination, Aug. 20, 1940. Late that afternoon, seated at this table, Trotsky was felled by an alpine pickax wielded by a Spanish communist named Ramon Mercader.

Eight wax Ediphone cylinders on the table preserve the last recordings of the voice that once roused millions with its oratorical power. Here, too, are the writing tools -- pens, ink bottles, an old-fashioned "rocking blotter" -- of this advocate of world revolution. On the uncluttered desk are a few personal items: a magnifying glass, an ivory letter opener, a Japanese lacquered box, a seashell.

On a tray in front of his straight-back wicker chair are Trotsky's shattered tortoise-shell eyeglasses, smashed during the fierce struggle with his killer.

The overloaded bookshelves along the wall sag under countless titles in Russian, German, French and English. Trotsky was fluent in all these languages, and his collection of books spans a broad spectrum of subjects. But above all, Trotsky was a dedicated Marxist, and the shelves hoard the complete works of Karl Marx, Friedrich Engels and Vladimir Ilyich Lenin. His multi-volume set of the Great Soviet Encyclopedia surely gave him no satisfaction when he read the government-approved version of his role in Soviet history. He was judged an anti-party conspirator who committed grave ideological errors, a counter-revolutionary against whom Lenin bitterly fought.

In the far corner of the room is a little cot on which Trotsky, often yielding to the Mexican heat and his doctor's orders, took siestas.

The heat of Mexico took some getting used to for the Trotskys, who grew up with the harshness of Mother Russia's winters. When Stalin ordered Trotsky deported from the Soviet Union in 1929, he and Natalia wandered from Turkey to France to Norway, drifting until an offer of permanent residence came from Mexico: The celebrated artist Diego Rivera, an admirer of Trotsky, had interceded with the Mexican president.

The master bedroom, protected by a metal door, is sparely furnished with a double bed covered by a serape, a commode and poignant photos of a youthful Trotsky. Piles of aging newspapers and magazines, stored here for years and now moved to his study, indicate Trotsky's eclectic reading choices: Pravda, the New York Times, Socialist Call, Figaro, Militant.

On the wall above, still clearly visible, the grisly pattern of machine-gun fire is imprinted on the pockmarked walls. This was the bedroom where Trotsky and Natalia awoke in the early hours of May 24, 1940, to find themselves under attack. A band of armed men had overcome the policemen on duty outside the house. One of Trotsky's private guards had then opened, or been forced to open, the heavy iron entrance door, and the raiders charged in with machine guns.

Trotsky and Sedova, dazed and awaiting the worst, crouched on the floor behind the bed while the hail of bullets ripped through the room. In the adjoining bedroom, Seva, Trotsky's 14-year-old grandson, dove under his bed as bullets splattered around him. Twenty minutes later the attackers withdrew, but not before planting a dynamite bomb in the garden. Miraculously, although Trotsky, Sedova and Seva were slightly injured, no one in the household was hurt seriously; the bomb failed to go off.

The only fatality was the guard who'd opened the entrance gate, a young New Yorker named Robert Harte. He was kidnapped by the assailants; a month later, Harte's body was found in the basement of a farmhouse. When the plot was finally unraveled by police, the principal organizer turned out to be celebrated Mexican muralist David Alfaro Siqueiros. Siqueiros, a founder of the Mexican Communist Party and an ardent pro-Stalinist, was arrested along with two dozen others. He later fled to Chile and did not return until four years later, to claim immunity under the statute of limitations. He was never brought to trial.

After the onslaught, Trotsky's "little fortress" of Coyoacan reinforced its defenses. Walls were made higher, more watchtowers were built, steel shutters were affixed to windows, and armor plating applied to the doors. Inside the now-sealed entrance gate, Trotsky placed a marble plaque: "In Memory of Robert Sheldon Harte, 1915-1940. Murdered by Stalin."

Even while the Trotsky stronghold was being fortified, a new visitor stood by in the garden one day watching the construction work. Ramon Mercader, using the name Frank Jacson, had become the companion of Sylvia Agelof, a young woman from Brooklyn who occasionally did secretarial work for Trotsky. Mercader, bearing gifts and doing frequent favors, slowly but surely ingratiated himself with the household.

On Aug. 20, 1940, Trotsky's copy of Ultimas Noticias, his favorite Mexico City newspaper, headlined critical developments of World War II, then raging in Europe. Beleaguered Britain was making urgent pleas for increased aid from the Uniteds States. Churchill wanted 50 aging American destroyers for his hard-pressed Navy. The Nazis were stepping up daylight bombing of London. In the United States, Congress was about to adopt a compulsory military service bill.

For Stalin, it must have seemed a good time to rid himself of his old enemy. The attention of the world was focused on momentous events. If the Nazis were victorious over Britain, Stalin knew the might of the German army would be turned on him. Trotsky, the exiled "traitor" and still a potential rival, had to be eliminated.

Mercader asked Trotsky to do him a favor: He had written a political article, he said, and wanted Trotsky to look it over. In Trotsky's study, Mercader seated himself at the table. While Trotsky pored over the manuscript, Mercader delivered a fatal blow to Trotsky's skull with a mountaineering ax. Trotsky screamed and grappled with his assassin, toppling over chairs and bookshelves. At the moment of the assault, Trotsky had a small revolver within reach, and an electric alarm button at the edge of the table to alert his guards. But Mercader had positioned himself so that Trotsky was unable to reach the gun or the little black button.

Trotsky's guards eventually captured and subdued Mercader. Trotsky was rushed to a nearby hospital, where he died the next day.

For five days his body lay in state while hundreds of thousands of people came to pay their last respects. His ashes were laid to rest in the leafy garden on the site of the hutches where he had spent many hours tending to his beloved pet rabbits.

In 1960, Ramon Mercader was released from prison after completing a full 20-year sentence for the murder of Leon Trotsky. He fled to Moscow, where he was awarded the title of Hero of the Soviet Union. He died in 1977. The Leon Trotsky Museum and House (Viena 45, at the corner of Avenida Viena and Calle Morelos in the Colonia del Carman area of Coyoacan) is open Tuesday to Friday, 10:30 a.m. to 2 p.m. and 3 to 5 p.m., and on weekends from 10:30 a.m. to 4 p.m. Guided tours are available with advance notice.

Jack Goldfarb is a freelance writer who lives in New York and London and travels extensively.