The tower was built on soft ground composed of clay and fine sand, and originally its foundations were less than 10 feet (3m) deep. The tilt became obvious in the early stages of building as the foundation couldn’t compensate for the soft ground, and for a long time construction was put on hold - partly because of the tilt, but mostly because Pisa was involved in a lot of wars with its neighbors. By the time construction resumed, the building had mostly stabilized, but over the centuries the tower gradually leaned more and more in one direction. In the late 19th and early 20th centuries, the tower was stabilized. Today the tilt is about 3.97º, but before the stabilizing efforts of the last centuries, it was 5.5º.