The town is still surrounded by more than 9 kilometres of ancient walls, mainly built in the 15th and 16th centuries.Together with those of Lucca, they are the best preserved Renaissance walls in Italy.
The most iconic building of the town is the imponent Castello Estense: sited in the very centre of the town, it's a brick building surrounded by a moat, with four massive bastions. It was built starting in 1385 and partly restored in 1554; the pavilions on the top of the towers date from the latter year.
The ancient City Hall, renovated in the 18th century, was the earlier residence of the Este family. Close by it is the former Cathedral of Saint George, begun in 1135, when the Romanesque lower part of the main façade and the side façades were completed. According to a now lost inscription the church was built in 1135 by Guglielmo I of Adelardi (d. 1146), who is buried in it. The sculpture of the main portal is the signed work of the "artifex" Nicholaus, mentioned in the lost inscription as the "architect" for the church. The upper part of the main façade, with arcades of pointed arches, dates from the 13th century, while the lower part of the protiro or projecting porch and the main portal are by Nicholaus. The recumbent lions guarding the entrance are replacements of the originals, now in the narthex of the church. The elaborate reflief sculptures depicting Last Judgement gracing the second story of the porch above date from the thirteenth century. The interior was restored in the baroque style in 1712. The campanile, in the Renaissance style, dates from 1451–1493, but the last storey was added at the end of the 16th century.