Silver ingot fragments with coins showing a portrait of Athena, the patron goddess of the city; the reverse side shows an owl, a symbol of Athens. The Laurium silver mines, south of Athens may have been worked as early as 1000 BCE, but in 483 BCE Athenians exploited the veins to finance construction of a large fleet, which then defeated the Persians at Salamis in 480. Sparta forced the closing of the mines after their occupation of Decelea in 413. Production remained low until after 350, when, as Demosthenes speeches show, large fortunes were being made by the proprietors. The Laureot Owls, Athenian silver coinage attributed to the mines, were circulated throughout the Classical world, but by Roman times the mines lay neglected because of competition from the gold and silver mines of Pangaeum in Macedonia and piratical raids on the Laurium mines.