Built in the ancient era, the Parthenon was extensively damaged by earthquakes. Also, during the Sixth Ottoman–Venetian War (1684–1699) against the Ottoman Empire, the defending Turks fortified the Acropolis and used the Parthenon as a castle. On 26 September 1687, a Venetian artillery round, fired from the Hill of Philopappus, blew up the Parthenon, and the building was partly destroyed. The explosion blew out the building's central portion and caused the cella's walls to crumble into rubble. Three of the four walls collapsed, or nearly so, and about three-fifths of the sculptures from the frieze fell. About three hundred people were killed in the explosion, which showered marble fragments over a significant area. For the next century and a half, portions of the remaining structure were scavenged for building material and looted of any remaining objects of value.