The center of Helsinki is home to a bit of mathematics history, in the form of a pavement consisting of kite and dart shapes. The pavement was the result of a cool math contest.
The challenge was to provide a mathematical proof of the minimum number of shapes that could be fit into a pattern that was flat (with no gaps or overlap), tessellating, and infinitely varying. The riddle was solved by the mathematician Roger Penrose, who proposed just two simple shapes – a kite and dart. Winning the contest involved receiving a contract with a tile company to produce the pattern. Unfortunately, the pattern never became a best seller.