The Iron Floor is a floor you can build (the Iron kit).
In-game description
Plates of blued iron over flagstones. On an upper story, also the ceiling below.SHOWN IN THE BUILD RING
Building it
It costs 1 
Stone, 1 
Iron Ingot, 1 Earth spirit. It needs 3 Jewels first. Take it down with DISMANTLE to get its cost back (see Building).
