The Floating Man's Quarry

Floating Man Quarry is a location in Rosewood, Pennsylvania. It was first mentioned in Unbelievable when Mona tries to kill Spencer there; but Spencer, in an act of defence, ends up pushing Mona to her death instead.

Ali's Pretty Little Lies
Courtney DiLaurentis, posing as her twin sister Alison, develops a huge crush on Nick Maxwell. She gives him her number and, supposedly weeks later, out on a date, he blindfolds her. He surprises her with a picnic at Floating Man's Quarry. During the picnic, overwhelmed by the fact 'Courtney' (really Alison) is returning, she reveals she has a twin (without telling him her twin is the real Alison) and Nick offers comfort and support.

Unbelievable (Book 4)
Mona Vanderwaal drives Spencer Hastings to Floating Man's Quarry after revealing she is A. Outside of her car, Mona tries to convince Spencer to become A with her, saying they could pin it on someone else. Spencer refuses and Mona attacks her, trying to push her into the quarry. Spencer, trying to defend herself, pushes Mona into the quarry instead. Police pull her out dead and with a broken neck.

Ruthless (Book 10)
Spencer's ex-friend Kelsey Pierce, who she used to get high with at Penn over the summer, returns as Emily's new love interest. Emily is hurt by Spencer's remarks about her love for  Alison, she angrily tells Kelsey that Spencer framed her for the drug possession when they were both arrested. Depressed, Kelsey overdoses and attempts to throw herself into Floating Man's Quarry, where  Mona  died, but Emily saves her and Kelsey is sent to the Preserve  for treatment.