A room floored with pennies. Never heard of such a thing until yesterday, but now I want one.
There are various ways to do a penny floor. They all seem to produce gorgeous results and, if you discount the DIY labor of installation, are fairly cheap as floorings go (about $2.88 per square foot in pennies plus some adhesives and coatings).
Most of the objections raised here are easily answered. Except the one about … oops, metal being conductive. So, you science-minded types: would a penny floor, well covered with an epoxy coating, threaten life & limb? The phrase “to die for” leaves me a little uneasy in this particular case.