The patron saint of Certaldo is Saint Thomas the Apostle, celebrated on 3 July in the church dedicated to him, overlooking Piazza Boccaccio next to the town hall. Between the 11th and 13th centuries, meanwhile, the church of Santi Tommaso e Prospero arose at the oldest point of the medieval village, now deconsecrated, with its attached convent and cloister, along Via Rivellino, the village's oldest street, which linked the fortification atop the hill to the Via Francigena.
Certaldo is famed above all as the town where Giovanni Boccaccio died and, in all likelihood, was born, in 1313, living there steadily in the last years of his life and dying there with certainty in 1375. His house, still open to visitors along Via Boccaccio, the main street of the upper town that already existed in the 13th century, was almost entirely destroyed by bombing as the front passed through during the Second World War and rebuilt right after it. Certaldo Alto, also reachable by a rack-railway funicular from Piazza Boccaccio, still preserves today its 14th-century town walls with their three historic gates, while on the nearby Poggio del Boccaccio hill an Etruscan-Hellenistic chamber tomb and the remains of an ancient Etruscan settlement have been found.
