Here is a set of laser-cut Truchet tiles with circular arcs, designed to be rearranged in a frame. The top layer parts with the quarter-circle arcs are glued to the squares of the bottom layer. The rule when assembling the tiles is to match high to high and low to low.
With just these two types of pieces, you can make a variety of patterns ranging from only circular islands to only circular lakes, with many possible landscapes in-between. Because the surface is raised, you can make rubbings with a pencil or crayon to save your favorites to paper.
More: See all of George Hart’s Math Monday columns