The Leaning Tower of Pisa may have found some new competition. Big Ben in London, the most identifiable landmark, has been recorded as having a tilt of 0.26 degrees. This tilt of one foot off the vertical is said to be visible to the naked eye, but is not a cause for alarm. “We’re talking about unbelievably small movements,” said John Burland, an engineering professor at Imperial College London who has been involved in the study of the tower.

At the current rate of 0.9mm a year, Big Ben will reach the tilt of its competitor, the Leaning Tower of Pisa, in around 4,000 years. The Leaning Tower of Pisa is currently recorded as being tilted four degrees, or 12 feet off the vertical.

While the clock tower has been off-center since it was erected in the mid-nineteenth century, the accelerating tilt is partially the effect of constant underground construction underneath the landmark. These would include the sewer systems, an underground car park, and the Jubilee line station. Other factors such as seasonal temperature and moisture level changes could also be factors of the accelerated tilt.

The movements of Big Ben have caused cracks in the walls of the other parts of the tower, affecting the office of ministers in the House of Commons.