In the
Greater Boston Area, "the pit" usually referes to a specific place in
Harvard Square, in the
People's Republic of Cambridge (aka just
Cambridge).
As you exit the subway station (from one side), the stairs come to a landing. About 15 feet ahead is another set of stairs, going up about 3 or 4 steps. This set of stairs wraps around the entire enclosure (except for a ramp to allow handicap access - this is the People's Republic of Cambridge afterall). This comprises "The Pit". It is outdoors, it is small. There are people (often called "pit kids" for lack of a better term) who hang out there.
As far as I can tell - they just sit there all day. They are almost exclusivly white, teenagers. I would guess with an average range of 14 to 20. They tend to look like a standard band of what you might classify as "punk" - at least as far as I am able to tell.