Rocca di Offagna, Medieval fortress in Offagna, Italy.

Rocca di Offagna is a massive quadrilateral fortress on a fortified tuff crag, built between 1454 and 1456 by Lombard masons for the Republic of Ancona. Its thick brick walls, pierced by about 50 bombard positions, were meant to resist firearms, and the battlements are Ghibelline swallowtail. A five-level keep stands at the centre of the small courtyard, and a semicircular tower still closes the north-east stretch of the outer walls.

The Maritime Republic of Ancona built this fortress between 1454 and 1456 to defend its territory against the rival city of Osimo. Its construction reflects the political tensions and military needs of the Adriatic region during the Renaissance period.

The keep's alarm bell, dated 1477, carries an invocation to the Madonna and the signature of its founder, Iacobus de Istria. Since restoration the fortress has housed a collection of antique weapons assembled with the Accademia di Oplologia e Militaria of Ancona and the State Museums of San Marino, alongside temporary exhibitions.

The visit to the Museo della Rocca covers the whole structure, including the patrol walkway and the terrace on top of the keep, reached by stairs. From there the view runs over the Marche hills and historic centres, from the Apennines to the Conero riviera. The keep has five levels and the original wooden stairs and drawbridges are gone, so access is by stone steps.

The castellan's residence on the third floor contained the fortress's only chimney, reflecting his elevated status within the structure. Access to the keep was intentionally positioned on the fourth floor to enhance the building's defensive strength.