Tre Colli is a hamlet along the provincial road 56 up to the Monte Serra, near Castelmaggiore. The latter was the castle of Calci (1222) in a dominant position on the Arno plain, where an archiepiscopal residence, known as the ‘villa dell’arcivescovo’ (1120), stood. The most important building in Castelmaggiore is the early medieval Church of San Michele Arcangelo, mentioned as early as the 19th century in the documents of the Badia di San Savino.
Tre Colli is crossed by the Zambra stream and is overlooked, in addition to Monte Serra, by the other two major peaks of Monte Pisano: Monte Cascetto (902 m) and Monte Pruno (872 m).
Here is the parish church dedicated to St Bartholomew and attested since the 13th century. It was one of the sixteen medieval branch churches of the Pieve dei Santi Giovanni ed Ermolao (in Calci). Its bell tower was built on the ruins of one of the towers of the town wall, destroyed by the Pisans during the wars against Lucca.
The parish church is in Pisan Romanesque style with a stone façade. Inside, there is a unique baptismal font, a wooden crucifix and a Madonna delle Grazie, much venerated by the locals, so much so that the church has taken the name of Sanctuary of the Madonna delle Grazie.
Every year, a handcrafted nativity scene (presepio) is set up in the church to recall the traditions and trades of the ‘Valgraziosa‘, the valley for which Calci was once famous both for its beauty and for the presence of numerous mills along the streams