So you thought you knew the Thames ...

In countless walks along the Thames over the last 30 years, since it stopped being a major commercial waterway, I can scarcely recall a time when I have not spotted something new and surprising. The process of making London's river more visitor-friendly has been going ahead undramatically - a bit here and a bit there - but to good effect.

We can now walk along the south bank almost the whole way from Tower Bridge to beyond Lambeth Bridge on a dedicated riverside path. Along it, the old commercial buildings have either been pulled down or turned back- to-front, to present their best faces to the river. It is an intriguing walk that reveals much about the history of the Thames and its city.

The section just west of Tower Bridge is one of the newest parts of the walk, opened only in the last few months. It gives unrivalled views of the Tower on the opposite bank and next to it the classical river front of Smirke's 1825 Custom House.

This is the sixth Custom House on or near this site: the poet Geoffrey Chaucer was a customs officer in one of them in 1374. It was the only place for levying duties when ships crowded in here to unload supplies for the markets around Cheapside, before the docks were built farther east in the 18th century.

Next to it is the old Billingsgate fish market, signalled by the flying fish on its weathervanes. A Roman jetty excavated here is evidence that this was London's main berthing area from the time the Romans founded the city in the 1st century.

You have to climb to the road at London Bridge, then down the other side to Southwark Cathedral, formerly St Saviour's Church, parts of it dating from the 12th century. Go inside to see the fine medieval memorials. From here the route takes you briefly through atmospheric narrow alleys, where it is easy to miss one of the most surprising of the river bank's hidden attractions. The magnificent stone tracery of the 14th-century rose window of the medieval palace of the Bishops of Winchester is now reinstalled in its old position on a high wall above the palace's excavated foundations.

The walk passes beneath a railway bridge to reveal, next to Southwark Bridge on the north bank, the 1989 headquarters of the Financial Times, a pleasing bronze box with copious vegetation inside the tall central atrium. We walk under Southwark Bridge Approach to reach the 17th-century Anchor Inn, with a platform for riverside drinking and a view of the dome of St Paul's.

Beyond the inn is the reconstructed Globe Theatre and at Cardinal's Wharf a 17th-century house reputed, without much corroboration, to be where Wren lived when his cathedral was being built, to keep an eye on the work in progress.

Bankside Power Station, to its west, was completed only in 1960 and is already redundant, but will shortly be born again as an extension of the Tate Gallery, and there is talk of a footbridge to link it with St Paul's. Next to it the Founders' Arms, a pleasant modern pub, is on the site of the foundry where the cathedral's bells were cast.

A walkway is being built beneath Blackfriars Bridge approach, but for the time being you have to climb to the road again, walking back down the steps between the river and Doggett's Coat and Badge, a pub named after the annual race for oarsmen. Look at the width of the river here and imagine how broad it was before the embankment was built: you can then understand why no attempt was made to build a second bridge in London until the mid-18th century.

Gabriel's Wharf is now on the left, an enclave of small restaurants and designer shops for textiles and jewellery. You can hire a bike here by the hour or the day, for more energetic sightseeing.

Walking on, we reach Denys Lasdun's unfairly maligned National Theatre (1976). Outside it, and just under Waterloo Bridge, is one of London's best second-hand book markets.

Beyond the bridge and the Royal Festival Hall the river bends south. On the opposite bank Cleopatra's Needle, carved about 1500BC and thus older than London itself, was erected here in 1878. Further on is Terry Farrell's playful creation on top of Charing Cross station.

After Hungerford Bridge, Jubilee Gardens on the left is temporarily overwhelmed by construction works for the Jubilee Line extension. Between here and County Hall, keep your eyes down and read the isolated paving stones etched with verses about London by the likes of Wordsworth, Spenser, Spike Milligan and William Morris ("The clear Thames bordered by its gardens green").

The proposed conversion of County Hall into a Japanese hotel and conference centre appears to be stalled: it stands as a forlorn memorial to Margaret Thatcher's abolition of the Greater London Council, whose home it was.

After crossing Westminster Bridge Approach, look back to see the South Bank Lion that once stood outside a nearby brewery. It is made of Coade Stone, an 18th-century artificial stone whose formula was for years a closely kept secret.

Now the walkway goes behind St Thomas's Hospital - notice the dolphin motifs on the lamp standards - with a dramatic view of Parliament.

On your left, Lambeth Palace, home of the Archbishop of Canterbury, is the only one of the great medieval riverside mansions to have survived in central London. Beyond it, dreary modern office blocks line Albert Embankment, the site of the Lambeth Delftware potteries, one of London's principal industries in the 17th and 18th centuries. Barges would bring clay up the river here from East Anglia.

A choice collection of Delftware drug jars can be seen in the lobby of the Royal Pharmaceutical Society, opposite Lambeth Palace at the corner of Lambeth High Street.

In the 19th century, the large Doulton works continued the pottery connection. Doulton moved away in 1956 but one of its old buildings remains, tucked away on the corner of Black Prince Road and Lambeth High Street, with wonderfully detailed tiling and terracotta work. It is worth seeking out.

The open space farther on, behind the railway line, is the site of the former Vauxhall Gardens, London's premier pleasure grounds for nearly 200 years from 1660, where Handel's music was performed, Hogarth's work displayed and romantic assignations were made.

Millennium funding is being sought for an imaginative scheme to recreate a modern version of Vauxhall Gardens on the site. If that goes ahead, it will continue the gradual reclamation of the river.

Michael Leapman is the main contributor to the Eyewitness Guide to London (Dorling Kindersley, pounds 14.99).

The best way to arrive is still by boat, on one of the services that run from Westminster, Charing Cross or Tower piers. As you approach, the tall masts of the 19th-century sailing clipper Cutty Sark, dwarfing Sir Francis Chichester's Gipsy Moth IV alongside it, create the right nautical atmosphere, and this is sustained in the extensive National Maritime Museum, a few hundred yards away.

A large weekend market is packed with stalls selling crafts, clothes and antiques. There are good bookshops, an enterprising theatre and one of the London's few surviving eel and pie houses. The riverside Trafalgar Tavern was the scene of 19th-century "whitebait dinners," where prominent politicians and lawyers celebrated great events by feasting on locally- caught whitebait - long since driven away by pollution.

Wren's twin-domed Royal Naval Hospital makes London's finest vista when viewed from the other bank of the river on the Isle of Dogs: Canaletto is one of many artists to have depicted it. The former hospital is in two halves so as not to interrupt the river view from the Queen's House, built for the wife of James I and the first Palladian-style work of Inigo Jones, now restored to pristine condition.

Behind it, Greenwich Park may also soon be brought back to its former elegance. On top of the hill is the Old Royal Observatory, part of it by Wren, from where the world's time is measured.

St Alfege Church, by Wren's pupil Hawksmoor, commemorates the Archbishop of Canterbury taken hostage by invading Danes and murdered here in 1014.

If you have time, it is worth continuing the trip down river to see the curious metal cowls of the Thames Barrier, opened in 1984 to protect London from an invader just as implacable as the Danes - the ever rising tides.

HMS Belfast

Second World War cruiser moored opposite the Tower and fitted as a museum of naval history. Children love to swivel in the gun turrets, 10.30am- 5.30pm daily.

Old Operating Theatre

A few minutes from the riverside walkway, squeezed between London Bridge Station and Guy's Hospital, this was the theatre of the original St. Thomas's Hospital until it moved west in 1862. It is fitted out as in the 19th- century and there is a gruesome depiction of surgery in the days before anaesthetics. Open Tuesday-Sun, 10am-4pm.

Clink Museum

On the site of the notorious Clink prison, alongisde the Bishop of Winchester's London residence, this is a no-holds-barred museum of crime, punishment and prostitution: for centuries London's best brothels, or "stews" were here. The museum is open daily, 10am-6pm.

Shakespeare's Globe

On a site 200 yards from the original Elizabeth theatre, an exact replica of it is being built. The three-tiered thatched gallery, made of oak timbers, is already in place and the first public performances will be held here next summer. Guided tours and an explanatory exhibition, 10am-5pm daily.

Museum of the Moving Image

A superb interactive exhibition about film and television, popular with children, stands alongside the National Film Theatre. Strolling costumed actors help you find your way and there are plenty of viewing areas where historic film clips are shown, 10am-6pm daily.

Florence Nightingale Museum

Near the entrance to St. Thomas's Hospital, this museum is easy to miss but is worth hunting for. Many original documents and dramatic displays illustrate the career of the "Lady with the Lamp" and explain the impact she made on nursing. Open Tue-Sun, 10am-4pm.

Museum of Garden History

Just outside Lambeth Palace, the 14th-century St. Mary's church has been converted into a museum of compulsive interest to gardeners. A Jacobean knot garden has been created in the churchyard, near the tomb of the John Tradescants, the father and son who were Britain's leading plant hunters in the 17th and18th centuries. Open Mon-Fri, 10.30am-4pm, Sun 10.30am- 5pm.