For most of its roughly 2,500-year history, the Parthenon was a functional building. Originally a temple to Athena built in mid-5th century BCE, it was later converted into a Byzantine church, a Roman Catholic cathedral, and then a mosque when the Ottoman Empire conquered Greece in 1458. In 1687 a Venetian cannonball detonated the gunpowder the Ottomans had stored inside the Parthenon, leaving the building largely in ruins.