The Hearth

From Callahan's Wiki

The Hearth at alt.callahans is known to have been a-periodically tiled (perhaps by Mary, Mike Callahan's daughter, in a less Iron-mongering mood) using a single Penrose Tile... While certain progress has been made in producing such a tiling in what is laughingly known as the Real World (tm), the kinks in the trick have not yet been completely Iron-ed (in the "God is an Iron" sense) out...