Conquered by the Etruscans, Castiglione del Lago was put under the jurisdiction of nearby Chiusi and for many centuries was called "Castrum Clusii" (castle of Chiusi). After the Roman period, the marshy land in the area was reclaimed and connected with the Valdichiana. In the Middle Ages it became a powerfully fortified village; the Castle was built, destroyed and rebuilt, until Frederick II of Swabia had it razed and rebuilt again (13th century), transforming it into a fortress called 'Castello del Leone' (Castle of the Lion), which later became "Castiglione." It was a marquisate from the 16th to the 17th century, and then became a duchy under the Della Corgna family. When the Della Corgna dynasty died out in the 17th century, Castiglione del Lago became the property of the Papal States, until the Unification of Italy (1860). ART, CULTURE, ENVIRONMENT
The historic center is surrounded by medieval walls with three gates: Porta Fiorentina, Porta Senese and Porta Perugina. There is an impressive fortress, the Rocca del Leone, one of the most interesting examples of medieval Umbrian military architecture. Built in 1247 to a design by Fra' Elia Coppi da Cortona, it has the shape of an irregular pentagon, with five towers and three gates, dominated by a triangular main tower nearly 30 meters tall. The walkway offers splendid views of the lake, and the vast space inside is used today as a natural amphitheater for shows and events. Another building of great artistic importance is the Ducal Palace or Palazzo della Corgna, commissioned by Ascanio della Corgna in 1560 and designed by Vignola or Galeazzo Alessi. The interior is sumptuously decorated with frescoes by Salvio Savin and Niccolò Circignani, known as "Pomarancio," with scenes from mythology and of the military exploits of the condottiere Ascanio della Corgna. Together they represent one of the best examples of Mannerist painting in Umbria. Also worthy of a visit are the Church of Santa Maria Maddalena, with a fine panel from 1500 by a student of Perugino, a Madonna of the Milk by the Sienese school of the 1300s, and frescoes by Mariano Piervittori (1850); the Church of San Domenico di Guzman, with a splendid wooden coffered ceiling and an ambulatory used as a the tomb of the Della Corgna family; and, on the village's main square, Piazza Mazzini, the 13th-century Palazzo del Capitano del Popolo. In the vicinity of Castiglione del Lago are numerous Etruscan settlements scattered among the small villages built on the surrounding hills, at Gioiella, Vaiano, Pozzuolo and, near Panicarola, the Sanctuary of Madonna della Carraia (proto-Villanovian necropolis). Built in the 17th century, the sanctuary has a spacious interior with a Greek cross plan and a fine wooden altar with the venerated image of a Madonna and Child. Of great natural and environmental interest is Polvese Island, the largest in Lake Trasimeno, designated as an oasis with facilities and an educational-environmental park. The island is covered with thick vegetation, with ilex, laurel and pubescent oak groves, and is an excellent place for observing animals.