Free Gold: The Forgotten Mine of Arothand

In a 20' × 20' chamber within the Deep Dwarven Mine of Arothand is every ounce of gold dug from the Heart of a Mountain.

1,280,000 ounces of gold ÷ 16 ounces × 10cn = 800,000gp

The mine workings themselves are no less than 16,843 10' × 10' ×10' volumes of mined space yielding no less than one ounce of gold per ton. So a chamber 160' high x 160' wide × 160' long with towering in situ pillars to prevent the mountain from crumbling.

Its guardians are a dwarven vampire, cavern predators, A Dwarven army of stone statues, and the occasional multi-ton (20d6 damage) block of stone.