Interior of the Basilica di San Petronio, Bologna, Italy. The church hosts also a marking in the form of a meridian line inlaid in the paving of the left aisle in 1655; it was calculated and designed by the famous astronomer Giovanni Domenico Cassini, who was teaching astronomy at the University. A meridian line does not indicate the time, but instead the day of the year and also meridian lines were used to accurately determine the length of the solar year. At 66.8 metres it is one of the largest astronomical instruments in the world, allowing measurements that were for the time uniquely precise