In Italy, well-known travertine quarries exist in Tivoli and Guidonia Montecelio, where the most important quarries since Ancient Roman times can be found. The Guidonia quarry has major historic value, as it was one of the quarries where Gian Lorenzo Bernini selected material from which to build the famous Colonnade of St. Peter's Square in Rome (colonnato di Piazza S. Pietro) in 1656-1667. Michaelangelo also chose travertine as the material for the external ribs of the dome of St Peter's Basilica. Travertine derives its name from the former town, known as Tibur in ancient Roman times. The ancient name for the stone was lapis tiburtinus, meaning tibur stone, which was gradually corrupted to travertino (travertine). Detailed studies of the Tivoli and Guidonia travertine deposits revealed diurnal and annual rhythmic banding and laminae, which have potential use in geochronology.