Hephaestus' Cabin is constructed of brick, and has a smokestack sticking out of it, mimicking a tiny factory. The entrance is like a vault door, circular and made of thick metal. It opens with much turning of gears and hissing smoke. The cabin has glossy metal walls and metal slatted windows.
It is noted for being unclean and messy, and is often filled with junk and miscellaneous items. The interior of cabin consists of steel bunks folded against the walls, which lead down to private rooms, with a digital control panel. It has a basement filled with power-tools, an assortment of weapons, workbenches, and stacks of scrap metal. There is a tunnel underneath it that leads to Bunker 9, as well as a large tunnel system under Camp Half-Blood.