From the Iron Man bio page:
“Stark Tower is built 1 mile off the coast of Manhattan. Between tidal, geothermal, and fusion plants Stark tower is a net contributor to the Manhattan power grid. Tony claims the top 10 floors of Stark Tower as his own. Stark Tower is relatively inexpensive to rent space in and has no outside power, sewage, or water needs.”
The Tower is connected to the mainland by a sophisticated magnetic rail system, which regularly shuttles commuters to and from Grand Central Terminal.
Tony’s private labs and the offices of his VP of Operations Pepper Potts occupy the top floors of the Tower.
The monorail was sabotaged and the Tower attacked by the armored mercenary known as the Titanium Man as part of the plot by Hydra to strike at the world’s security infrastructure. (Assembly Required #1)