Julia Solis' excellent new New York Underground: The Anatomy of A City (Routledge, 2004) delves into every aspect of subterranean NYC - from analyzing urban legends (alligators, mole people and much more) to a detailed history of the trains, steam tunnels, and much weirder spaces under the buildings and streets of this city. The book is very well illustrated, and is more a tour of the various underground systems of the city than any kind of dry academic analysis. Solis is an accomplished photographer, and her creepy and haunting images - abandoned train stations, cathedral crypts, subterranean hospital passageways - will stay with you long after you put the book down.