Formerly the USS Intrepid, this 900-foot aircraft carrier is serving out its retirement as the centerpiece of Manhattan's only floating museum. An A-12 Blackbird spy plane, lunar landing modules, helicopters, seaplanes, and other aircraft are on deck. Docked alongside, and also part of the museum, are the Growler, a strategic-missile submarine; the Edson, a Vietnam-era destroyer; and several other battle-scarred naval veterans. Children can explore the ships' skinny hallways and winding staircases, as well as manipulating countless knobs, buttons, and wheels. For an extra thrill (and an extra $8), they can try the Navy Flight Simulator and "land" an aircraft onboard. COST: $14; free to active U.S. military personnel. Subway: A, C, E to 42nd St.; M42 bus to pier.