The construction of the Collegiate Church of Saints Lorenzo and Leonardo of Castelfiorentino, originally dedicated only to Saint Leonardo, dates back to approximately the 13th-14th century, in the central part of the encastellation. The identified position wanted to seal the important relationship established with the nearby municipal structure, as the magistral authorities swore allegiance there in the name of God.
The building has been built in Romanesque-Lombard style, with late adhesions to the Gothic, in terra cotta bricks that, in a few places, signal a disposition or a particular decoration that surely succeed in lending a sense of movement; the wall that runs along via San Lorenzo still has circular oculi and bricks placed with a fishbone shape, in addition to preserving a cross built in scratched bricks, set in such a way that it appears as a bas-relief.
On the same side there is the bell tower, once with a sail-like structure and demolished in 1692 to be rebuilt on the tower model, showing two shelves with their belfry and a small terrace on the third level, with a three-bell cell.
The interior has a ceiling made of wooden trusses, brought back to light after renovation works in 1923; of the seven original altars only three remain today, each one placed in a different nave. The central altar held the remains of Saint Verdiana, the patron saint of the city, now transferred to the sanctuary of the same name.
Among the works housed there are a 14th-century crucifix, eight ovals made by Giovanni Camillo Sagrestano narrating the Stories of Saint Verdiana and three paintings by Annibale Gatti, Glory of Saint Verdiana between St. Anthony, St. Blaise, St. Hippolytus, St. Lawrence Martyr and St. Donato Bishop of Arezzo, The funeral of Saint Verdiana and Clement VII praying in the church of Saint Verdiana.
To the name of St. Leonardo was added that of St. Lorenzo in memory of the expulsion of the troops of Arrigo VII, which took place on August 10, 1313.
The Collegiate Church, initially dedicated only to St. Leonardo, was consecrated also to St. Lorenzo in memory of the expulsion of Arrigo VII and his army, on the day of St. Lorenzo, August 10, 1313.