The Leaning Tower of Pisa and its 5.5 degree lean have vexed engineers for centuries. Partially constructed on unexpectedly soft soil, the ancient bell tower began to lean before it was even finished, a historical goof that went on to become one of the world's historical oddities — and made the tower a UNESCO World Heritage site.

How can something so obviously structurally unsound endure in an earthquake-prone region for hundreds of years? People who assemble an IKEA cabinet and have 18 pieces left over don't expect to pass a wobbly Hemnes down to their great-grandchildren.