How deep are the New York sewers and are there maps?

Having just watched C.H.U.D., it occured to me to wonder: How far down do the sewers and tunnels under the Big Apple go? Are they accurately mapped by anyone?

      • Well yes they are mapped, but who is allowed to look is mainly utility providers looking for the last few ways to string cable through steam tunnels. They don’t just let everybody look at them. Many of them are nearly impasable with various cabling; some companies have found it is cheaper to put in cellular phone service now than try to add land-lines in some big US cities like NY.
  • On a related note, I understand that for a hi-rise building, genereally, the basement is 10% of the above-ground height. So for a 100-story building, you could potentially have a building 10 stories deep…
  • There are however, fansites on the web detailing old subway maps and routes, for cities all over the world such as NY and London. Due to recent events, the NY ones might now be secured to a greater degree than in the past (we would hope, anyway).
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