My favourite place in Washington is not on the ground. It is up in the sky, in a window seat on the left side of the plane, as you land at National Airport (or Reagan National Airport to give its full name, which still irritates most of the 550,000 residents of this overwhelmingly Democratic city).
It may be one of the most spectacular airport approaches on earth – a sweep down the rocky and foaming Potomac river that still carries a hint of untamed frontier, then the final turn and the sudden unfolding below of the imperial city: the State Department and Federal Reserve buildings, then the White House half hidden by trees, the white needle of the Washington Monument, then the Capitol, and finally across the Potomac, now flat and wide, at an impossibly low height, before touchdown itself.
Part of the pleasure, of course, is returning home. But there's also the enduring thrill of arriving in a city that combines the grandiose and the intimate as few others. I've spent 14 of the past 18 years here, and in that time Washington has turned from government enclave to world-class city. As recently as 1991, politics was the only topic of conversation at a dinner party. Now the place is a genuine metropolis with neighbourhoods, shopping, restaurants and cultural amenities to match, and history at almost every turn.
Not so long ago, the infamous Washington of crime, muggings and drugs started a bare five blocks from the White House. Today, affluence and gentrification are marching eastward. Even the old segregation of the city's predominantly white western half and black eastern part is breaking down a little, and the age of Obama will surely hasten the process. We've even got a decent sports team. "First in war, first in peace and last in the American League," the old joke ran about Washington. Now the ice hockey Capitals are the best show in town, albeit thanks to a posse of Russian and Swedish stars. That's what being an imperial city does for you.
Imperial cities, moreover, boast great vistas, and great monuments to the presidents, generals and ordinary men who have shaped their history. These, too, are part of Washington's appeal. They are centred on the mile-long green carpet of the Mall that runs through its ceremonial heart from the Capitol to the Lincoln Memorial, never a more powerful symbol than as the first black president prepares to take office. Like every imperial city, Washington is a place of power, spies and scandal. And, of course, there's the politics.
The visitor to Washington doesn't need to seek out politics. Stick around, and it will come to you, never more so than during an inauguration with up to 2 million visitors in attendance. Indeed, if you don't like crowds, overbooked hotels and sold-out restaurants, politics may be too much of a good thing this week. And do not imagine that when the hubbub subsides, you'll be able to rub shoulders with the new president or peek into where he lives.
In this post-9/11 era, unless you know someone important, the old guided tours of the formal rooms in the White House residence are no more. You might find yourself within a few yards of Obama – but only when he speeds past in one of those motorcades that are an accepted daily annoyance of Washington life, behind the black bullet-proof windows of a limousine (and you don't even know which of two identical limousines is actually carrying him). Then there are the helicopters, another symbol of the urgency of power. Our house in north-west Washington happens to be almost directly under the Marine One flight path from the South Lawn of the White House to the presidential retreat at Camp David in the Maryland mountains. But again, which of three helicopters is the one?
A better bet is the other end of Pennsylvania Avenue, where a spanking new underground visitors' centre has been opened at the Capitol. If Congress is in session, the Senate gallery when a vote is happening is the place to be. They vote by personal roll call, so you can see how short and stocky John McCain is in real life, and that the greying thatch of the previous presidential loser, Democrat John Kerry, truly is a wonder of the hair stylist's art. But the real charm of Washington is the off-duty encounter with the famous. The city is for political junkies what Hollywood is for movie stars – except that you've a much better chance of getting up close and personal.
Politicians build careers on reviling Washington. ("Government is not the solution, but the problem," Ronald Reagan used to say.) But when the time comes to leave, surprisingly many of them don't. In Washington, a face a few tables away in a hotel bar looks vaguely familiar – and then you realise it belongs to a former director of the CIA. Sometimes I stood waiting for my car at my parking garage alongside fellow customer George McGovern. It took me a while to get over queuing up to pay behind the 1972 Democratic presidential nominee.
Washington's appeal lies in such human moments, in everyday places associated with people who once wielded vast power. Some are landmarks, such as Ford's Theater on 10th Street where you can see the box where Abraham Lincoln was shot, and Petersen House, across the road, where he died. The theatre is being refurbished and will reopen next month. On S Street is the handsome neo-Georgian house where Woodrow Wilson spent the last three years of his life. It is one of my favourite places in the city, with its perfectly preserved 1920s interior and furniture, and personal memorabilia that bring the austere 28th president back to life.
Less than a mile away, next to the Potomac, is the somewhat ugly Watergate building, for ever associated with the downfall of Richard Nixon. Sadly, the old Howard Johnson hotel where the burglars set up their HQ is now a university dorm. But hang around on Virginia Avenue outside, in the small hours of a warm June night, and skulduggery at the highest level of government is in the air.
No presidential sites are more poignant than those associated with JFK. On N Street in Georgetown stands the three-storey 1812 house where the young senator and his family lived before moving into the White House. I can't walk past St Matthew's cathedral where his funeral took place without thinking of John Jnr as he saluted his father's coffin. Across the river in Arlington Cemetery is his grave, alongside those of his wife, his brother Robert, and two infant children, one of them stillborn.
Arlington is one of Washington's great places. It's best on a cold wintry day, when visitors are few. The lines of identical, immaculately tended, white marble gravestones bespeak the sacrifices of America's wars. You find some unexpected names there, such as Joe Louis and Lee Marvin, buried almost next to each other in plot 7-A, not as champion boxer and Hollywood star but as army sergeant and US marine.
We British have a stake in Arlington, too, in Field Marshal John Dill, Churchill's top military representative in Washington and an unsung architect of Anglo-American co-operation in the Second World War. He is one of a handful of foreigners buried in America's national cemetery, his grave marked by an equestrian statue. Most unforgettable of all, you may just happen on a formal burial as it takes place. As the heels of the honour guard click on the hard pathway, and the coffin is laid to rest in silence, time stands still.
But presidents and politics are only two of Washington's hallmarks. Another is espionage, an industry in which it indubitably leads the world. Everyone wants to learn their most powerful enemy's tricks, none more so than the former Soviet Union. Maclean, Burgess and Philby were just three who practised their trade here, based in the former British embassy chancery that is now the ambassador's residence.
In Georgetown, at the old Au Pied de Cochon restaurant that is now a Five Guys burger bar, a brass plaque marks the booth of the "last supper" from which Soviet double defector Vitaly Yurchenko, a KGB colonel, fled his CIA minder on a November evening in 1985. Alas, they've now removed America's most infamous mail box, once not far away at 37th and R Street, on which the CIA super-mole Aldrich Ames left chalk marks to arrange dead drops for his Soviet controllers. It is now to be seen in the International Spy Museum, which has rightly become one of the city's top tourist attractions, even at $25 for admission.
Which brings me to arguably Washington's greatest boon, the spectacular array of free and dazzling museums: the Air and Space Museum, of course (and its terrific new adjunct out near the city's other airport, Dulles), but also the handsomely refurbished Museum of American History, and a host of others including Washington's wonderful zoo, all under the aegis of the Smithsonian Institution.
No, Washington doesn't have the buzz of London, the bustle of New York or the chic of Paris. But it's more livable than any of them; not small enough to be boring, not large enough to overwhelm. It also happens to be where more decisions that shaped history, for better or worse, have been taken over the past century than any other city on earth. We residents tend to forget such things – except when you're sitting in a plane about to land at the heart of it all.
Tourist information (020-8339 6048; www.usembassy.org.uk/rctour.html);
Ice Hockey Capitals (001 202 628 3200; www.verizoncenter.com);
Capitol Visitor Center (001 202 226 8000; www.visitthecapital.gov);
Senate Gallery (001 202 226 8000; www.senate.gov/visiting/common/generic/visiting_ galleries.htm);
Ford's Theater (001 202 233 0701; www.nps.gov/foth);
Petersen House (001 202 233 0701; www.nps.gov/foth );
Woodrow Wilson House (001 202 387 4062; www.woodrowwilsonhouse.org); Watergate building, 2600 Virginia Ave NW;
JFK former family home, 3307 N Street, Georgetown;
St Matthew's cathedral (001 202 347 3215; www.stmatthewscathedral.org);
Arlington Cemetery (001 703 607 8000; www.arlingtoncemetery.org);
Five Guys, 1335 Wisconsin Ave NW;
International Spy Museum (001 202 393 7798; www.spymuseum.org);
Air and Space Museum (001 202 633 2214; www.nasm.si.edu);
Museum of American History (001 202 633 1000; www.americanhistory.si.edu);