Nearby, Trafalgar Square is another vibrant people zone.

And, overlooking it, is the National Gallery, with London's greatest collection of European paintings. The National Gallery lets you tour the sweeping story of European art without ever crossing the Channel.

From medieval altarpieces — which told Bible stories in rich, yet two-dimensional detail — art enters the Renaissance.

Here the Italian master Crivelli pulls out all the stops to show realistic detail while portraying the annunciation. Notice the playfulness he employs to show off his mastery of 3-D. From the foreground you go back, back, back, and then…bam! you've got a pickle in your face.

And Renaissance painters revel in pre-Christian classical scenes. Here, another Italian master, Sandro Botticelli, paints Mars taking a break from war…succumbing to Venus and the delights of love, while impish satyrs play innocently with the discarded tools of death. It was the dawn of the Renaissance, and there was an air of playful optimism.

Leonardo da Vinci takes Mary and Jesus out of the gold leaf never-never land of medieval altarpieces, and brings them right down to a real world we can relate to. Leonardo's subtle play of light on the faces is masterful.

And the National Gallery's delightful sweep through art history continues: From Baroque with dramatic fantasies (this one thanks to Rubens) — to frilly Rococo decadence. Impressionists like Renoir capture the breezy ambience of a boat ride, and Cézanne takes us to the brink of the modern world.

Many of London's top sights front the River Thames, which has become a transportation thoroughfare for tourists. We're sailing from Westminster, under Big Ben, to the Tower of London…enjoying an informative narration with the views.

Narrator: Somerset House, built over 200 years ago, was a private residence for the earls and dukes of Somerset.

Tower Bridge looks medieval, but it was actually built with a steel skeleton in 1894 in faux-medieval style to match its famous neighbor just a few steps away.

The Tower of London goes back to the Norman Conquest.

William, Duke of Normandy, became William the Conqueror when he crossed the English Channel in 1066 and took the throne of England. To help establish his rule, he had this awesome — and really awesome-in-its-day — fortress built.

Its purpose: put 15 feet of stone between him and his new subjects. This original tower — the White Tower — gave the castle complex its name. The style of the age was Romanesque, which the English call “Norman” for the invaders who imported it.

This charming chapel of St. John — dating to 1080 and one of the oldest in England — provides a rare look at pure Norman architecture: round Roman-style arches and thick walls.

You'll see an intimidating collection of medieval weaponry and armor. Your entry includes a peek at the most dazzling crown jewels in Europe — no cameras allowed — and an entertaining tour with one of the Yeoman Warders — or “Beefeaters.”

Beefeater: Please to note this is still a royal palace. Although no longer a royal residence, we should not lose sight of the fact that all of our kings and queens, they lived here for more than 500 years.

The tower marks the oldest part of London — a district called “The City.” Today this is the financial center of Britain. But these days bank headquarters fill shiny skyscrapers and many of the elegant original bank buildings survive as fancy pubs — their vaults now filled with kegs of real English ale.

In pubs you order at the bar. Lager is the cold carbonated American-style beer. Ales and bitters are the more traditional English choice. Only confused tourists leave a tip.

While the Tube takes me on long jaunts underground, buses are great for quick hops. And, when armed with my cheap all-day transit pass, buses work perfectly for hopping on and off between sights. Take advantage of public transit, and London gets much easier.

In a move to alleviate its notorious traffic problems, London levies a “congestion charge” on private cars entering the city center. This leaves the streets mostly to taxis and buses. Things move along a little quicker, and money raised helps subsidize public transit: more departures and cheaper fares.

Somerset House, a grand 18th-century civic palace, now houses several fine galleries and museums.

The Gilbert Collection displays some of the best in European decorative arts.

Snuffboxes are a highlight. These contained powdered and scented snuff tobacco — a craze among the aristocracy in 18th-century Europe. These fancy little boxes were popular as gifts. Diplomats and royalty gave them away like jewelry. A fashionable man would have a different snuffbox for every occasion.

Frederick the Great owned over 300 boxes. His best — while considered part of the Prussian crown jewels — are here in London. This one, from 1765, is mother of pearl, studded with precious stones and a profusion of diamonds.

Micro-mosaics are another exquisite art form from the 1700s. These were souvenirs for aristocrats making the Grand Tour. Scenes featured their favorite sights — like postcards tourists pick up today. Rome was the most popular destination featured. Made from thousands of tiny fragments, the pieces are so intricate that the museum provides magnifying glasses. To adorn their jewelry, wealthy women brought mosaics home, where their favorite jeweler fashioned them into delights such as these.