|“||This is A's lair.||”|
A's lair is "A's" base of operations. It is where "A" would go to think of plans, send texts, create messages, and find ways to torture the girls.
In the Season 2 finale, it is revealed to be located in Room 2 of the Lost Woods Resort. The room contains pictures, newspaper clippings, and dolls resembling the girls and Alison. There is a hole in the wall behind a picture frame so "A" could watch Alison in Room 1 next door. This is where Spencer figures out Mona is "A," due to the gum wrapper and cashmere sweaters. It is also where Mona reveals herself to be "A" and knocks Spencer out.
In the Season 3 premiere, "It Happened 'That Night'," it's revealed that when the girls came back to the lair the morning after the masquerade ball, the room was empty. They didn't tell Emily about it until 5 months later. Over these months, Spencer had been visiting the empty room in order to create a computer-generated 3D representation of the way it had been when she first saw it.
The new "A" searches for a new place to create his/her lair beginning in "The Remains of the "A"," when he circles a classified ad for a room for rent. At the end of "The Kahn Game," "A" rents the apartment (Room A), and moves in at the end of "What Lies Beneath."
The new lair, complete with all the photos and paraphernalia taken from Mona's Lost Wood's lair, is revealed during "The Lady Killer" when Mona is seen talking to the new "A."
In "Dead to Me", It is revealed as apartment A in a block of apartments on Mayflower Hill. Spencer finds the second lair, but "A" has realized that the liars now have the key, and has relocated, leaving the room empty.
In "Will The Circle Be Unbroken?", "A" is seen looking at a poster of Rosewood's Carnival at Rosewood Town Center, then "A" closes the laptop and "A" is seen opening the blinds of a mobile home and then driving it throughout Rosewood.
In "A DAngerous GAme", we see two (now former) members of the "A-Team", Mona and Spencer in the mobile hideout of "A".