La Rocca, surrounded by a lawn, is located in the heart of the small and characteristic historic center of San Martino in Rio in Emilia: with a quadrangular plan it preserves a square corner tower, with Ghibelline battlements.
Belonging to the Canossa family, the Roberti family, then to the Este family and finally to the Marquis Paolo Rango d'Aragona, it now houses the Museum of Agriculture and the Rural World, the Coppelli Art Gallery, the Civic Library, the Historical Archive and the Open Archive for Henghel Gualdi.
Inside, the most significant rooms are: the 15th century Chapel of San Giovanni, built in 1395, which still retains the terracotta bands of the portal, the apse and the original altar in Verona marble with the sandstone coat of arms of the Roberti da Tripoli and a valuable San Martino, also in sandstone; and some rooms with painted chests, frescoes and stuccos dating back to the 15th-18th centuries. In the heart of the Torrazzo the unicorn room stands out: on the fourteenth-century structure, Borso d’Este commissioned the tempera decorations in the mid-fifteenth century: in this period some painters from the Erri family work. The representation tells about some "enterprises" of the Este house, including the mythical animal.