The leaning tower has never really been straight. Not long after work began in 1173, the foundation settled unevenly, and the tower started inclining toward the north. When constructioh continued, after a nearly 100-year hiatus, the building shifted again, so that by 1272, it was visibly leaning south. Today the top of the tower is 5.227 meters off-center, tilting southward. Throughout the monument's history, architects and engineers have attempted to halt the lean, but since regular monitoring began in 1911, the offset at the top of the tower has increased at a fairly consistent rate of about 1.2 millimeters each year. Fears about the safety of the landmark became acute when a similarly constructed bell tower at the Cathedral of Pavia collapsed suddenly in 1989. Shortly thereafter the tower at Pisa was closed to visitors. ln 1990 a special commission, composed of Italian and foreign experts in the fields of structural engineering, geotechnical engineering, history of art and restoraton of monuments, was brought together by the Italian government to determine new ways to save the tower. The group I work with, the Consorzio Progetto Torre di Pisa (the Tower of Pisa Project Consortium), has supervised several projects that have stabilized the structure and slowed the rate of its incline. Initial efforts focused on the exterior of the tower, but in the next few months, we plan to try other, more radical techniques to halt the tower's lean. These methods will be applied direstly to the soil, modifying the monument's footing. Large-scale field trials are now under way at the Piazza dei Miracoli (Miracle Square), where the tower stands, but all work is berng done far from the monument itself. We must guard against the possibility that altermg the ground too close to the tower could eventually damage the building. Our ultimate goal is not to straighten the tower. Because the strueture tilted in different directions during the early stages of construction, it became curved like a banana and will never stand truly upright. Instead we hope to ease its top back some 10 or 20 centimeters. With luck, our efforts will keep the landmark standing into the next century, when a new generation of scientists will tackle the 800-year-old problem of the leaning tower of Pisa.
