Italy’s Leaning Tower of Pisa lived up to its name right from the start, as it began to tilt early on in the construction process. The foundations were laid on August 9, 1173, but work came to a halt as builders reached the fourth floor in 1178. This was in part because the iconic landmark began leaning slightly atop the muddy soil — which was too soft to begin with and settled unevenly under the tower’s weight — and in part due to an ongoing war between Pisa and nearby city-states. When construction recommenced in 1272, the tower was tipped at a roughly 0.2-degree angle, though the soft ground had compacted enough that work could continue. In order to compensate for the lean, new floors were built with one side taller than the other, thus giving the tower a unique curve, though the structure continued to slowly tilt even further.
Construction of the tower’s bell chamber began in 1360, by which time the tower was tilting at a 1.6-degree angle. The Leaning Tower of Pisa was officially completed in 1372, though it took several centuries for its seven giant bells to be installed. Centuries later those bells were stilled, as experts feared that their repeated movement was contributing to the tower’s increasing tilt. By 1990, the tower leaned 5.5 degrees to the side, necessitating the installation of counterweights. While the Leaning Tower of Pisa was originally designed to stand nearly 197 feet tall, it now only reaches a height of 186 feet at its highest point, and 183 feet at its lowest.