The symbolic heart of London, St. Paul's will take your breath away. In fact, its dome -- the world's third largest -- will already be familiar, since you see it peeping through on the skyline from many an angle, riding high (although now nudged by skyscrapers) over the rooftops of the City, just as it does in Canaletto's 18th-century views of the Thames. The cathedral is, of course, the masterpiece of Sir Christopher Wren (1632-1723), completed in 1710 after 35 years of building and much argument with the Royal Commission, then, much later, miraculously (mostly) spared by the World War II bombs. Wren had originally been commissioned to restore Old St. Paul's, the Norman cathedral that had replaced, in its turn, three earlier versions, but the Great Fire left so little of it standing that a new cathedral was deemed necessary.

Wren's first plan, known as the "New Model," did not make it past the drawing board; the second, known as the "Great Model," got as far as the 20-foot oak rendering you can see here today before it, too, was rejected, whereupon Wren is said to have burst into tears. The third, however, known as the Warrant Design (because it received the royal warrant), was accepted, with the fortunate coda that the architect be allowed to make changes as he saw fit. Without that, there would be no dome, because the approved design had featured a steeple. Parliament felt that building was proceeding too slowly (in fact, 35 years is lightning speed, as cathedrals go) and withheld half of Wren's pay for the last 13 years of work. He was pushing 80 when Queen Anne finally coughed up the arrears.

When you enter and see the dome from the inside, you may find that it seems smaller than you expected. You aren't imagining things -- it is smaller, and 60 feet lower than the lead-covered outer dome. Between the inner and outer domes is a brick cone, which supports the familiar 850-ton lantern, surmounted by its golden ball and cross. Nobody can resist making a beeline for the dome, so we'll start beneath it, standing dead center, on the beautiful sunburst floor, Wren's focal mirror of the magnificent design above.

Now climb the 259 spiral steps to the Whispering Gallery. This is the part of the cathedral with which you bribe children, who are fascinated by the acoustic phenomenon: whisper something to the wall on one side, and a second later it transmits clearly to the other side, 107 feet away. The only problem is identifying "your" whisper from the cacophony of everyone else's. Look down onto the nave from here, and up to the frescoes of St. Paul by Sir James Thornhill (who nearly fell off while painting them), before ascending farther to the Stone Gallery, which encircles the outside of the dome. Up again (careful -- you will have tackled 627 steps altogether), and you reach the Golden Gallery, from which you can view the lantern through a circular opening called the oculus and walk outside the roof.

Back downstairs there are the inevitable monuments and memorials to see, though fewer than one might expect because Wren didn't want his masterpiece cluttered up. The poet John Donne, who had been Dean of St. Paul's for his final 10 years (he died in 1631), lies in the south choir aisle; his is the only monument remaining from Old St. Paul's. There is Wren's own memorial, with an epitaph by his son (who also worked on the building) that reads succinctly: lector, si monumentum requiris, circumspice (reader, if you seek his monument, look around you). The vivacious choir-stall carvings nearby are the work of Grinling Gibbons, as is the organ, which Wren designed and Handel played. The painters Sir Joshua Reynolds and J. M. W. Turner are commemorated, as is George Washington. The American connection continues behind the high altar in the American Memorial Chapel, dedicated in 1958 to the 28,000 GIs stationed here who lost their lives in World War II.

A visit to the crypt brings you to Wren's tomb (also with his son's epitaph), the black marble sarcophagus containing Admiral Nelson (who was pickled in alcohol for his final voyage here from Trafalgar), and an equestrian statue of the Duke of Wellington on top of his grandiose tomb. A café and gift shop are also in the crypt. Finally, to catch Wren's facade and dome at its most splendid, remember to make a return trip to see St. Paul's at night. COST: Cathedral, crypt, ambulatory, and gallery £6. Tube: St. Paul's.