In Roman times it was known as Insula Romana, because it rather looked like an island surrounded by the waters of the Lacus Umber, a large body of water that occupied the Umbra Valley which, in the 6th century CE was most likely a drained marshland.
It was very important in the 14th-15th centuries when, as a fortified city, it was continually contested by Perugia and Assisi. Perugia won, in the end, and Bastia became a feudal holding of the ruling Baglioni family until it died out in the 17th century. In the mid-1600s it went to the Papal States, which ruled over it until the Unification of Italy in 1860.
ART, CULTURE, ENVIRONMENT
Although the town has a modern look, one can find evidence of its history in an old castle, of which many traces remain, and in various religious buildings, like the 14th century Church of the Santa Croce on the main Piazza Mazzini. It has a characteristic pink and white limestone façade made with stone from Mt. Subasio and is home to lovely frescoes of the Umbrian school and a triptych done by Niccolò Liberatore, known as l'Alunno. Also worth noting are the Church of San Michele Arcangelo, the Church of San Rocco, home to two canvases by Dono Doni, and the Church of San Paolo (11th century), once a Benedictine monastery in which St Claire sought refuge. Porta Sant'Angelo is also lovely, the only gate that corresponds with the western part of the castle. It is well-preserved and has a pointed arch and crenulated corbels.
Not far away, in Santa Lucia and Bastiola, are the bridges over the Chiascio River. Also of interest is the Church of the Madonna di Campagna and, in Costano, the Church of San Francescuccio, the temple of San Giuseppe and the Sanctuary of the Santissimo Crocifisso.