In the early 1300s, the Leaning Tower of Pisa was built as a bell tower for the Cathedral of Pisa. The tower was built on a slope and gradually started to lean due to the weight of the bells and the church it was attached to. In 1990, scientists from the University of Pisa used a sophisticated laser scanner to measure the lean of the tower, which had been slowly increasing over the centuries. By 2006, the tower was 13.7 degrees off vertical, and by 2009 it was 18.3 degrees off vertical. In 2010, the tower was officially closed to the public and the Italian government began an exhaustive restoration project that will last until