The museum complex of Palazzo dei Priori is located inside the thirteenth-century palace of the same name that stands out on Piazza del Popolo. The building, the result of annexes of a private house and the ancient church of San Martino, took on its current appearance only in the sixteenth century with the imposing access staircase and the imposing bronze statue of Pope Sixtus V cast in 1588 by Andrea Sansovino when Fermo becomes an archiepiscopal seat.

Inside there are the Civic Art Gallery, the Sala del Mappamondo and the Representation Rooms which include: the Hall of Portraits, the Hall of Costumes, the Hall of Coats of Arms, the Hall of the Mayor, the Sala dell'Aquila with the precious frescoes by Pio Panfili and the Red Room.

The Civic Art Gallery houses an important collection of paintings from the Marche and Veneto schools, together with stone artefacts, costumes, coats of arms, porcelain, furnishings and valuable objects. Among the most significant works are those of Andrea da Bologna, Francescuccio di Cecco Ghissi, Jacobello del Fiore (Stories of Saint Lucia), Vittore Crivelli (Crucifixion), Vincenzo Pagani, Giuliano Presutti and Giovanni Lanfranco (Pentecost). Of particular interest is a Flemish tapestry made from a design by Giusto de Gand and the painting by Peter Paul Rubens depicting The Adoration of the Shepherds, commissioned to the painter in 1608 by the Filipino Fathers for their church. The precious "Sala del Mappamondo" commissioned by the Cardinal from Fermo Decio Azzolino j. and built in 1688 by the architect Adamo Sacripante, who preserves the oldest nucleus of the library. The Hall, fully furnished with walnut wood shelves, houses part of the ancient collection of the Municipal Library donated mainly by Romolo Spezioli, personal doctor of Queen Christina of Sweden. The imposing globe dominates the environment, created by the geographer Silvestro Amanzio Maroncelli in 1713.