Valindreth
Is there a diagram or description of the layout of HQ posted somewhere?
Uhhhh...no diagram yet.
This is what I personally use for the layout; some people think it's different:
The lobby is like a large foyer. Directly across from the door toward the back is a big staircase that goes up to the second floor. The second floor has that open balcony area and splits down the left and right halls that contain relatively large dorm-style rooms; 1 bedroom, 1 bath, no kitchen, maybe an outside balcony depending on if you're facing the backyard or not. There's a roof entrance at the very end of each hall.
Back to the lobby. On the right when you first come in is the general spot to hang out. There's couches, tables, chairs, etc. and a TV. Basically like a living room. To the left is the kitchen, large enough to keep all the kitchen stuff and some tables and chairs to hold about 8 people in one place (there's probably more tables/chairs, but that might be in another room; not sure though because it's never outright stated).
Still on the ground floor but toward the back/middle: There's a left wing and a right wing, both filled with corridors and rooms. The left has offices, a room where mission control used to be, and a large training room with plenty of equipment. The right has a small library, a bunch of storage rooms, and rooms that are for the most part empty.
At the very back of the ground floor, to the left of the giant staircase, there is a door to the back yard. To the right of the big staircase there is an entrance to the basement under the wall formed by the bigger staircase (someone else want to confirm something like this or have something different? the basement door was never clearly established)
The basement has a much smaller lobby of its own and splits off into more storage space, a wine cellar, and an interrogation room.
The backyard is pretty big and is surrounded by tall fence and hedges. There is a garden in the upper left corner (from the view stepping into the backyard) surrounded by shorter but similarly styled fencing. Some wall vines climb all the way up to people's balconies and are thick enough to be used as a makeshift ladder. There is no inset pool.