Note to Hamlet, 3.2.84: "Vulcan's stithy"

Vulcan's stithy: Vulcan's smithy. A smithy is a workshop with a furnace in which metals are heated before they are hammered into shape. Vulcan was a Roman god of fire, arms, and armor, and he was associated with volcanoes. 



The Forge of Vulcan by Diego Velázquez, (1630).
Image source: wikipedia: Vulcan (mythology)