The church has a 16th-century facade and a 12th-century body, but excavations have revealed the structure is actually five layers (and several more centuries) deep. It sits atop a much older Lombard church that served until the early 700s as Lucca's cathedral, which in turn was built atop a 5th-century-A.D. paleo-Christian church and 6th-century cemetery, which took the place of a Roman temple built atop Roman houses (from which some mosaic fragments survive). In the 9th century, a crypt was added. In all, 12 centuries of history jumble together in a confusing but interesting mélange beneath the pavement inside.