Furnace

A squat stone furnace, its belly kept at a heat that turns rock to liquid. Ore goes in raw and comes out as ingots — the first step of every smithing chain, and the reason a smithy is always the warmest building on the isle.

Smiths judge a furnace by how evenly it holds its heat rather than how fiercely it burns; a furnace that runs too hot ruins more ore than it renders.