The Fortified Marble Quarry was a quarry located in the middle of the Greek island of Paros during the 5th century BC. During the Peloponnesian War, it was transformed into an Athenian fort, and, in 429 BC, the mercenary Kassandra assaulted the fort to rescue the imprisoned Naxian admiral Euneas from Silanos of Paros' clutches. She also killed several soldiers, looted the quarry's valuables, and freed several prisoners.