After the Etruscans and the Romans, the town was destroyed during the barbaric invasions together with Pieve Santa Maria (the parish church), which rose on the remains of a pagan temple. It was reconstructed and dedicated to the Virgin Mary. The structure of the church is Romanesque and there are traces of frescos in the style of Giotto from the14th century and other 16th and 17th century paintings from the Florentine school. The massive belltower found on the side of the church is perhaps part of an ancient fortified complex that stood on the hill.
In the Middle Ages, together with the fortress of Belforte and that of Gattaia, Dicomano was sold to Florence in order to control the Wheat Route and the castles of the Count Guidi family. It later became an inland port for the supply of wood for the Pisa and Livorno shipyards. In the 18th century, Giuseppe Del Rosso realised the elegant Neo-classical Oratorio di Sant’Onofrio for the Dalle Pozze family. The interior is bright and particularly refined; it has a grey and white tiled marble floor, a dome and semicircular domes, and white marble decorations. The economic wealth of Dicomano grew under the Lorraine family and with the opening of the new road to Forlì (1824-1859).
The Archeological Museum of Mugello and Val di Sieve, found in City Hall in Dicomano, holds archaeological remains from the territory: sculptural masterpieces from the tombs of important families and elaborate jewels from Poggio Conca (Vicchio).
The Archaeological site in Frascole is a great square Etruscan structure, which is divided into three areas, stands. It is the mysterious “fortress” of the Velasna family and dates from 4th to early 3rd century B.C.. Some of the bricks inside the building, which are now being examined, may date back to an even more distant past. In summer the site hosts cultural events.