The precise location of the Hastings' Cabin is unclear, but it does not seem to be in Rosewood proper.
In "Save the Date," Hanna takes Caleb to the cabin without Spencer's family's permission; she seeks a secluded spot where Caleb's stalker won't be able to find them. While there, they remove the covers protecting the furniture and ignite the fireplace. It is later revealed that Hanna took Caleb here without Spencer's permission or knowledge.
In "A Hot Piece of A," Hanna throws Caleb a surprise party at the lake house. Spencer discovers that "A" had been in the attic and wonders if this is "A's" secret headquarters.
In "Let the Water Hold Me Down," Spencer shows the girls the items she found hidden in the attic - a handful of untraceable burner cell phones and a pack of gum.
In "It Happened 'That Night", after Alison's body is stolen from her grave by an unknown individual and the girls are set up to look guilty, the girls go to the cabin to have an alibi. Spencer leaves a note for her mother that says they have been there since that afternoon.
In the books, Spencer's family's cabin is where Alison is said to have died in a fire. Alison and the Pretty Little Liars had gone there when Alison confessed to having a doppelgänger. Alison had then sent fire to the house while the girls were inside, but they had managed to escape, including perhaps Alison.