Marble Arch subway complex (west) (London)

 tunnel, underpass, invisible, public toilet, underground facility

One third of one of the most complicated networks of pedestrian subways anyhwere in the world, with no fewer than 27 individual entrances and exits (some of which are now closed off).

This part of the network includes a large room that let passers by look at the huge pumps for the (now defunct) Marble Arch fountains (see the picture for an idea of the current state of these - the fountains themselves are visible to the east and have not worked for years), as well as toilets and decorative mosaics with a distinctly 1960s theme.

The complex was designed to make sure every section of what had been Hyde park (before Park Lane was turned into a dual carriageway, and the large gyratory was built round Marble Arch) remained accessible to the public - hence some of the curious and little-used exits that seem to go to nothing more than traffic islands. These subways were probably just a little bit too confusing, and are now due to be replaced with surface pedestrian crossings.

The other parts of this complex are immediately to the east, and the south.