The Duomo, the Cattedrale di Santa Maria del Fiore, is the central cathedral in town. There are numerous types of tours here. This is the central cathedral of the city. The church is good but the Baptistry is incredible. Reservations are a must for church tours. I also climbed the stairs to the top of the dome. It is quite a hike up but very ancient Italy. It's a tough climb but well worth it. At the top you have a 360 view of the city and it all carrera marble. It's spectacular.