Located on the main floor of the eighteenth-century Palace of the Counts Fossa Mancini, it opened on May 24^th 2003.

Visit the palace and have a tour in the various sections of the museum where you can admire the beautiful ceilings (one of which is decorated with festoons in neoclassical style), the entrance hall with stucco and baroque paintings of bucolic Arcadian setting, precious eighteenth-century furniture, a marble coat of arms of the House Fossa Mancini and a fresco of 1528 attributed to Andrea from Jesi and restored in 1998.

The area dedicated to the local ancient religious brotherhoods contains the amazing reconstruction of an altar whose objects belonged to the Tridentine rite.

Do not miss the section devoted to a valuable collection of contemporary graphic art donated by Brenno Bucciarelli (1918 – 1988), a famous art publisher born in Castelplanio. Here you can admire the prestigious works of some of the greatest artists of the twentieth century like Bruno da Osimo, Virgilio Guidi, Luigi Bartolini, Arnaldo Ciarrocchi, Primo Conti, Walter Piacesi along with some volumes of the Historical Archive containing the oldest manuscript dating back to the fifteenth century.