The fortress is built around a courtyard, with an old fountain.
A lot of elements overlook the courtyard: the building, leaning against the male, the building dedicated to cardinal Del Monte features spacious lounges (formerly service building); the entrance to the small chapel dedicated to St. John the Baptist and the majestic stairs to access to over forty rooms of the building. They meet also four towers with many courtyards and walkways.
The structure stands on several floors: a basement at various levels, a ground floor and a first variously articulated plan, the main floor and a mezzanine floor with large living room. It's surrounded by a sturdy wall, partly crowned by corbels, with corner buttress, formerly surrounded by a moat and a drawbridge on the southern slope. The idea began to outline a high, compact and dominating complex, on the massive plains of Gualdo Tadino.
Founded around the tenth century, as evidenced by ancient documents that origin from the Counts of Nocera, the castle was owned by Atti, Lords of Foligno, who held it until 1198 when it passed under the jurisdiction of Innocent III. At the beginning of the thirteenth century was the center of disputes between Gubbio and Perugia. In 1240, Frederick II, who stayed there for a long time, undertook the expansion and restoration of the fortress as well as the construction of the city walls, with four doors and seventeen towers.
The complex built that way represents the final version of the structure, which would thus had became the reference point for those who ruled the city of Gualdo Tadino. A plaque affixed on one of the towers testifies the permanence of Biordo Michelotti in 1394. Since then it was also called "Arx Maior Terre Gualdi" to distinguish it from the captain of the palace of the people called "Arx Minor". In 1434 the castle was given in vicariate to Count Francesco Sforza by Pope Eugenius IV; at the end of the same century it was transformed into illegal brand by the castellan of that period, Philip of Arcioni from Rome.
The old fortress, from 1513 up to 1587 housed the League Autonomous of Cardinals that hold the fate of the city, giving it a period of great splendor.
In order to fulfill the role of residence, the interior was modified and decorated with frescoes, of which, however, only a small part remains; during the mandate of the first cardinal legate, Antonio Ciocchi of Monte San Savino (1513-1533), the new aqueduct was built crossing the Flea fortress.
After 1587, with the entry of Gualdo Tadino in the District government of Perugia, the fortress became the official residence of the apostolic official until 1798.
In the nineteenth century it was destined to be women's prison for women of "immorality". Since the unification of Italy until 1985 it was for the male prison.
In the early '90s, the works of consolidation and restoration began, and they permitted the discovery of the primitive chapel of Sant'Angelo de Flea, at the base of the keep. They were also highlighted beautiful frescoes of the fourteenth and fifteenth century.
In 1996 the restoration was finished and the fortress was finally returned to the city and tourists. Since 1999 it houses the Civic Museum, a multimedia center, while inside the church there is the Antiquarium with archaeological finds documenting the population of the Gualdo territory from prehistoric times to the Middle Ages.