London is close enough to the North Sea to be affected by its tides, so the Thames’ level does indeed rise and fall twice a day. In fact, one reason the Romans found this a practical location to establish their city of Londinium — even though it was about 50 miles inland — was that their boats could hitch a free ride with the tides between the sea and the town twice a day. (I imagine oarsmen rejoicing.)

At low tide, the Thames’ beaches are littered with history. Today these exposed banks are red with clay tiles from 500-year-old roofs. Hefting a chunky piece of tile worn oval by the centuries, with its telltale peg hole still clearly visible, David points out how heavy these roofs were, which meant they needed stout timbers for support. In the 16th century, when ship-building for the Royal Navy made these timbers more in demand (and costly), lighter slate tiles became the preferred roofing material. Over time, the heavy red clay tiles migrated from the rooftops to the riverbank...and now into the pockets of beachcombers like us.

The stretch of river between the Tower Bridge (designed to be raised for ships) and London Bridge (which marks as far inland as seagoing vessels can sail) is nicknamed the “Pool of London.” In the 19th century, when “the sun never set on the British empire,” this was the busiest port in the world.

And in World War II, this part of London was targeted by the Nazis. Gesturing downriver past the Tower of London, David says, “In 1940 and 1941, Nazi bombers used the Thames as a guide on their nightly raids. When moonlit, they called it a ‘silver river of tinfoil.’ It led from the English Channel right to our mighty dockyards. Even with all the city lights carefully blacked out, those bombers easily found their targets. Neighborhoods on both banks of the river went up in flames. After the war, the business district on the North Bank was rebuilt, but the South Bank was long neglected.”

Turning his back to St. Paul’s Cathedral, David points to a vast complex of new buildings and continues, “Only now has the bombed-out South Bank been properly rebuilt. Our new Millennium pedestrian bridge connects the busy North Bank with the now trendy South Bank. There’s a real buzz in London about our South Bank.”

Despite the twin destructive forces of Nazi bombing and urban renewal, fascinating bits of the South Bank survive. Being careful to maintain our beachcombing curiosity (and not slip on the seaweed-covered concrete steps), we climb back up to street level and explore London’s South Bank.

Scaling steep stairs into a church loft, we find a crude surgical theater from the 1700s. Down the street, the last surviving turret of the original London Bridge is the decorative centerpiece of an old hospital yard. Since the days when merchants stopped here outside the walls of London to sell things tax-free, the still-bustling Borough Market has been where farmers meet city shopkeepers. We even pop into the quiet courtyard of a time-warp coaching inn. Looking up at the triple-layer set of balconies, David explains, “Courtyards like this provided struggling theater troupes — like young William Shakespeare’s — with a captive audience.”

Back at the embankment, overlooking the “Pool of London,” I pull out my pipe stem and imagine Charles Dickens blowing a little smoke. With the keen eye and curiosity of a beachcomber, you’ll come home with a pocket full of London history.

Rick Steves ( writes European travel guidebooks and hosts travel shows on public television and public radio. Email him at This email address is being protected from spambots. You need JavaScript enabled to view it. and follow his blog on Facebook.