1. Many of London's ancient lost rivers still through the city. This is the river Tyburn, which runs from Hampstead through Regent's Park and into the Thames.
2. This junction of two sewers near Stockwell tube station shows how beautiful much of the sewer network is.
3. This is an overflow sewer flowing into the Fleet sewer at Farringdon Street.
4. The sewer network is full of striking junctions like this.
5. This is where a sewer was dropped to a lower level during the building of the Metropolitan tube line, north of Hyde Park.
6. Here's a map of where the sewers are.
7. Meanwhile, the gargantuan Crossrail project has put a vast new layer of tunnels through London's underbelly.
8. The photographers behind the Subterranean London book accessed this National Grid excavation, part of the Crossrail network, by climbing down 12 storeys.
9. The Crossrail tunnels – seen here underneath Whitechapel station, 32 metres below street level – are vast and were built with a 150-metre-long boring machine.
10. The machine that made the tunnels weighs 1,000 tonnes and its cutting tool is seven metres across.
11. But perhaps the most remarkable part of London's hidden underground is its disused railway networks and stations.
12. Aldwych tube station shut in 1994. It was originally known as Strand and was used as an air-raid shelter during the Second World War.
13. There are occasional tours, and it's sometimes used for filming.
14. A train is stationed by one of the platforms for filming purposes, but the rest of Aldwych station has fallen into disrepair.
16. There are still instructions up for people using it as an air-raid shelter.
17. And old adverts.
19. Brompton Road station was once on the Piccadilly line, but was closed and later used as a military office. This map, which dates from the Second World War, shows gun placements across London.
Subterranean London, compiled by Bradley L. Garrett with a foreword by Will Self, is published by Prestel.