The Tower of Pisa began construction in the 12th Century but quickly began sinking and leaning to one side, so the builders in later centuries actually tried to correct the lean by building subsequent levels on a slight angle. It's now been locked in at a 5 degree lean by several tonnes of concrete poured into its base! Ryan spent a long time perfecting the round shape of the tower first before working out how to put it on a lean. The Tower contains nearly 42,000 bricks and took Ryan 127 hours to build!