Rocca Costanza, Military fortress in Pesaro, Italy.

Rocca Costanza is a fortress in Pesaro with a square plan and four cylindrical towers positioned at the corners. Straight walls connect these towers, and spiral staircases run through the interior spaces.

The fortress was built between 1474 and 1483 under Costanzo Sforza, with engineer Giorgio Marchesi da Settignano leading the design. It later served defensive purposes under different rulers, including when Cesare Borgia controlled the region around 1500.

The fortress's name comes from Costanzo I Sforza, who commissioned it. Since 2023 it has hosted summer events, festivals, concerts, and theatre and dance performances, while restoration for the Dario Fo and Franca Rame Foundation Museum and the State Archive is underway.

The fortress stands at the south-east corner of Pesaro's old walls, a short walk from the Adriatic shore, surrounded by pedestrian green spaces, a car park and a small park. Restoration work began in 2022 to house the Dario Fo and Franca Rame Foundation museum and the State Archive, so parts may be closed; in summer the building mostly hosts events, festivals, concerts and theatre and dance performances.

Around 1500, the fortress was surrounded by a moat filled with water from the Adriatic Sea, possibly on Leonardo da Vinci's advice during Cesare Borgia's occupation. This detail reveals how major Renaissance thinkers contributed to shaping this structure.