The Basilica of Santa Maria del Fiore commonly known as the Duomo is the cathedral church of the archdiocese of Florence It was originally designed to be the largest Catholic church in the world but the design was later scaled down Work began in but proceeded erratically until by only the dome for which the cathedral is most famous remained incomplete The dome built to a revolutionary octagonal design by Filippo Brunelleschi was completed in The campanile bell tower was designed by Giotto in the th century