Dragons lived in the Withered Heath beyond the Grey Mountains. Smaug was "the greatest of the dragons of his day", already centuries old at the time he was first recorded. He heard rumours of the great wealth of the Dwarf-kingdom of Erebor, which had a prosperous trade with the Northmen of Dale. Smaug "arose and without warning came against King Thrór and descended on the mountain in flames". After driving the Dwarves out of their stronghold, Smaug occupied the interior of the mountain for the next 150 years, guarding a vast hoard of treasure. He destroyed the town of Dale; the men retreated to the Long Lake, where they built Lake-town of houses on stilts, surrounded by water to guard against the dragon.