With a geology that makes it rich in natural springs, Hampstead is the source of three of London’s (now subterranean) rivers: the Fleet, the Tyburn and the Westbourne.

The River Fleet, or at any rate, its Hampstead branch, rises at Hampstead Ponds, where one of its streams is crossed by Hampstead Viaduct, a bridge to a housing estate that was never built. From South End Green, the river runs down Fleet Road to meet its Highgate branch and carry on towards King’s Cross and Blackfriars. The river is now buried underground but you can walk its route and there are still a few places where it’s possible to spot it. The sewer itself isn’t open to the public, but enthusiasts occasionally get to see inside it.

Goldington Crescent Gardens, inside a bend in the river’s course along Pancras Road, was once a water meadow called Pancras Wash that flooded when the river was high; a plaque set into the footpath commemorates the fact. At the southern end of Pancras Road, the curved façade of the Great Northern Hotel is shaped by what was once the bank of the Fleet, which then continued down King’s Cross Road and Farringdon Road and emptied into the Thames at Blackfriars. It still does that, under the road, but it will eventually empty into the new Tideway “super sewer” instead.

Along the King’s Cross Road, Farringdon Road and New Bridge Street, you’ll see that the streets on both sides head uphill, proving that you’re travelling along a river valley. It’s slightly less obvious at Ludgate Circus (where there was once a footbridge over the river called Bridewell Bridge), because the road level there has been raised, but Fleet Street is so called because it was the street that led down to the River Fleet.

Another Hampstead river, the Westbourne, rose at the long-gone Branch Hill Pond, flowing down to West End Green and on to Kilburn, which was originally just another name for the river. From there it continues through Paddington, where the hamlet on its west side, called Westbourne Green, gave its name to Westbourne Grove and Westbourne Park. It heads on into Kensington Gardens, where in 1730 it caught the eye of the queen consort (and sometimes regent) Caroline of Ansbach, who was keen to upgrade the gardens along with neighbouring Hyde Park. She therefore had it dammed (as opposed to damned) to create the Serpentine. A memorial to her now stands by the lake that she commissioned.

Sadly though, the Westbourne had become so polluted that, even by the beginning of the seventeenth century, its alias was “Ranelagh sewer”. In 1834 therefore, the Serpentine was hived off from the river/sewer, and now takes its water from boreholes instead, while the Westbourne was funelled into a culvert and continues its journey to the Thames largely underground. A Victorian iron conduit that carries the Westbourne can however be seen as it passes diagonally across the District Line above the platforms at Sloane Square station, before heading on to meet the Thames by Ranelagh Gardens in Chelsea.

Hampstead’s third river, the Tyburn rose at Shepherd’s Well, located just off Fitzjohns Avenue. It then heads south through Regent’s Park, where the boating lake was originally part of it (now, like the Serpentine, fed by boreholes) before winding its way through Marylebone and Mayfair – where, as Londonist have pointed out, wiggly streets on an otherwise perpendicular grid betray its route. The Tyburn passes under Oxford Street by Bond Street tube station, where an antique shop rather dubiously claims that it runs through their cellar.

Oxford Street was formerly called Tyburn Road, because it led to a village called Tyburn (where Marble Arch now is), which had a famous gallows, Tyburn Tree (a plaque on the site commemorates it), but it is not clear whether these names come from the Tyburn itself, or from a nearby (and unconnected) tributary of the Westbourne called Tyburn Brook. Meanwhile the Tyburn has something of a delta, splitting into four “distributaries” which enter the Thames at different places. At the main one, by Tyburn House at 140c Grosvenor Road, a plaque on the embankment marks the spot. The area between the distributaries, where Parliament and Westminster Abbey now stand, was called Thorney Island, and really was an island.

Hampstead had another important well too, the Chalybeate Well on Well Walk, whose iron-rich mineral waters made it a popular spa in the eighteenth century. Sadly, the fountain is now dry. Meanwhile, if you want to know why Hampstead is the source of all those rivers, blame it on all that Bartonian Bagshot sand and non-porous London clay, as we’ve already mentioned elsewhere in this very blog.