National Geographic has the most informative New York diagram that we've seen in lo these many years we've been working on Gothamist. It shows what is under the city streets-- both in a compressed, annotated form, and in a full-scale version (who knew the water tunnel was so deep underground? Stop lying, you totally didn't!) Definitely click around the diagram-- there's lots of delicious NYC facts embedded in the descriptions. For instance:
Consolidated Edison has 80,500 miles (129,524 kilometers) of underground cable that run virtually everything electrical in the city.
Each day 1.4 billion gallons (5.3 billion liters) of water flow into New York City from a series of reservoirs to the north.
We just wish that they had included all the CHUDs and Mole People-- because they don't get nearly the attention they deserve.