site of Monte d'Accoddi: a unique prehistoric monument with a step pyramid construction The Pisan City Walls that in the 13th century surrounded the city with 36 towers (at the moment only 6 remain), and the Catalan-Aragonese Castle named Castello di Sassari, demolished in 1877, whose ruins, including some rooms, the basement, and part of a tower were rediscovered in 2008. The church of St. Peter in Silki, built in the 12th century but renovated in the 17th century. Here were found the medieval codes known as Condaghe di san Pietro in Silki. Corso Vittorio Emanuele is the main street of the medieval town, surrounded by interesting buildings of different ages, such as several examples of Catalan-gothic (as the so-called House of Re Enzo), the baroque church of Sant' Andrea, built by Corsican community, the neoclassic Civic Theatre and Quesada's palace. The Cathedral of St. Nicholas of Bari, built in the 13th century and enlarged in Catalan Gothic style from 1480; there is a monument to the Duca di Moriana inside. The façade, belonging to the Baroque Spanish colonial restorations of 1650–1723, has a rectangular portico surmounted by three niches housing statues of saints. The bell tower is in Romanesque style. The church and monastery of Santa Maria di Bètlem (13th–19th century). The original façade and parts of monastery are in Lombard Romanesque style, some chapels in International Gothic, while the rest of the building, include the big dome, was rebuilt in Baroque and Neoclassic style, by the Sardinian architect Antonio Cano in 1829–34. The Church of the Most Blessed Trinity contains a beautiful picture by an unknown artist of the Quattrocento. The Cimitero comunale di Sassari (Sassari Cemetery) opened in 1837 adjacent to the Chiesa San Paolo al Cimitero just west of the main railway station Palazzo D'Usini, most important example of civilian architecture of the Renaissance period in Sardinia (now housing the main Public Library, therefore open to visits from the public). The Fountain of the Rosello, built in 1606 by Genoese craftsmen. It is made by two squared parts surmounted by two crossing arches supporting the statue of St. Gavino. University Palace (17th–20th century), originally a Jesuit school. The Ducal Palace (current Town Hall, 1775–1806), built for the Duke of the Asinara in the 18th century. Piazza d'Italia (19th century) is the main square in Sassari. It is surrounded by interesting buildings such as the Neo-Gothic "Palazzo