By hello
One of London's best-known lost rivers, the Tyburn rose in the Hampstead area and ran south through Marylebone and Mayfair before reaching the Thames. Its course is now underground, but the old valley still explains several irregular streets and subtle changes in level. Marylebone Lane is one of the clearest clues above ground, preserving a bend that does not fit the surrounding street grid because it followed the former line of the stream. Farther south, the Tyburn's route is echoed in Green Park, the edge of St James's Park, and the low ground toward Westminster and Pimlico.