Sleepy City is a website run by someone who (a) is a very good photographer and (b) enjoys sneaking illicitly into underground railway tunnels, drainage systems, abandoned buildings and the like, illegally taking gorgeous photographs and posting them online. Most recently, they posted
an epic feature on the Paris Métro, complete with some fantastic photographs:
Other galleries on the site include the tunnels (Underground and other) beneath London, explorations in the US, Russia and Japan, and a few evocative galleries from abandoned mental hospitals (always a good topic):
