The Parthenon itself replaced an older temple of Athena, which historians call the Pre-Parthenon or Older Parthenon, that was destroyed in the Persian invasion of 480 BC. The temple is archaeoastronomically aligned to the Hyades. While a sacred building dedicated to the city’s patron goddess, the Parthenon was actually used primarily as a treasury. For a time, it served as the treasury of the Delian League, which later became the Athenian Empire. In the final decade of the sixth century AD, the Parthenon was converted into a Christian church dedicated to the Virgin Mary.