Vietnam war obsessives, you surely know it. Sixties design fans, put a new shrine on your list.

The Vietnamese authorities perhaps didn't intend it, but their carefully preserved Independence Palace is a gem of period design - modernist political architecture and Goldfinger-era James Bond interiors - pleasing to both aesthetes and nostalgists. Officially, this squat concrete structure is "a national historical and cultural relic, a symbol of the victory that smashed the last stronghold of the US-backed Saigon puppet regime", as a museum director puts it.

I don't know if that works with Vietnamese people but, for me, unpropagandised and also a relic of the period, visiting the former presidential palace of the Republic of Vietnam, aka South Vietnam, is a much more complex affair, compounded of what I already knew and what I am witnessing first hand.

Yes, there is admiration for the heroic struggle, but there is also horror at the violence, disgust at the corruption and dejection at the waste. President Nguyen Van Thieu and his entourage lived here - their ghosts remain - but the place is light and airy, chiffon curtains billowing in cool breezes that fan the open-sided floors. And, wow, look at that amazing cocktail lounge in multicoloured leather - straight out of 1966 Bond parody Our Man Flint!

The war was brutal and tragic, and it was conducted from here by the South Vietnamese side, but the place stirs contradictory emotions, including rapture. Perhaps they shouldn't maintain it so well: the loving attention lavished on this monument piques my fondness for an era in which Jimi Hendrix's Purple Haze, not The Internationale, vibrated the surrounding streets.

On this site, the French built their grandiose governor-general's residence in the 1860s, in elaborate Second Empire style. From Norodom Palace, they ruled Cochin-China, as they termed southern Vietnam. In 1955, after the French had been forced out, Ngo Dinh Diem moved in, as president of the new Republic of Vietnam, and renamed it Independence Palace, but, in 1962, renegades in his own air force wrecked it in an assassination attempt by aerial bombing.

Diem then commissioned French-trained architect Ngo Viet Thu, winner of the prestigious Grand Prix de Rome, to build a completely new palace in a modern style. Young, handsome, romantic, Thu was the most famous architect in Vietnam, and an admired painter and poet: the right man for the job, without question. After all, who but Thu would give his nation's leaders a private meditation chamber with sweeping views of Saigon?

Thu designed the palace in Western modernist style but incorporated symbols that give it a subtle Indochinese spin. Most prominently, the balconied centre of the main facade mimics the Chinese character for "prosperity", and the building's T shape derives from the old Vietnamese character for "good destiny". More easily discernible, all along the front facade, stylised concrete pillars imitate a bamboo grove and shield the glass walls within.

The new Independence Palace, sometimes called the Presidential Palace, was inaugurated in 1966. Unfortunately, Diem didn't get to enjoy his new home; in the grave three years already, he had been shot in a 1963 coup and replaced by Thieu. Madame Nhu - Diem's sister-in-law and the de facto first lady of South Vietnam because of Diem's unmarried status - after choosing all the chandeliers, carpets and curtains for 95 rooms, must have been furious.

Thieu stayed here throughout the height of the war. On April 21, 1975, as the communist forces were homing in on Saigon, he fled. Then came the purblind seven-day president, Tran Van Huong, followed by the 43-hour president, General "Big" Minh.

I've done my homework, now for the footwork. I stroll the long, straight avenue that North Vietnamese Army (NVA) tanks rumbled down on April 30, 1975. I go through the wrought-iron gates the tanks smashed down, and skirt the lawn which they raked. I approach the long low facade with its "stone curtain" of pillars, I climb the grand central staircase the first NVA soldiers bounded up on that day to fly Hanoi's flag from the top-floor balcony.

On the second floor, I find the finest rooms, used for presidential offices and receptions, with decor varying from Vietnamese traditional to modern functional. On the desk of the president's office are three big phones, white, pink and red. Now, let me guess: the white one is for non-sensitive calls; the red is a secure hotline; and the pink, er, the pink is for his mistress? OK, then, you tell me.

The jewel is the Credentials Presenting Room, a gorgeous golden rendering of Vietnamese arts in square-formed, modernist style, with gold lacquered coffee tables and presidential desk, behind which the whole wall is a vast gold, brown and black lacquer mural of a historical landscape. This exquisite room, equivalent to an emperor's throne room in days of old, is deliberately located at the physical centre of the building, the official guidebook tells me. Quite right, too.

The third floor is the real 1960s deal, a relaxation zone with a cherry red plush cinema and a spacious entertainment room starring a circular leather sofa in beige and black, and a red-and-yellow Formica bar. I swear I can hear echoes of highball glasses clinking and Tony Bennett crooning I Left My Heart in San Francisco. Out through the screen doors, on the west wing roof, is the helipad, where a Huey stands ready.

One storey higher, on the main roof, is a pavilion with clear views all around and floor-to-ceiling windows that are left open to allow in the breeze. Called Tu Phuong Vo Su Lau ("peace in all directions"), this is the highpoint meditation room planned by Thu. However, the peace was shattered by Thieu, more oriented to nightlife than the spiritual life, who turned it into a discotheque.

Down to the basement, where the war rooms lurk, grim, grey and packed with 60s state-of-the-art communications technology, now extremely quaint. Yellowing maps plaster the walls, showing all the territory Thieu was about to lose. Desperation hangs in the air.

An information room shows the most poignant exhibit of all: a wire service photo from April 30, 1975, of communist troops haranguing the 43-hour president, not so "Big" Minh, slumped on a palace sofa. The crucial exchange is recorded as this.

Minh: "I have been waiting since early this morning to transfer power to you."

Colonel Bui Tin, of the NVA: "There is no question of you transferring power. You cannot give up what you do not have."

Later, they all sat down to a dinner of rice and NVA-ration canned beef - the first banquet of the new regime, in the Reunification Palace of Ho Chi Minh City.