Milan is the second most populated city in Italy but the first in economic importance; it is also one of the main financial and commercial centers of Europe. Milan is a major central hub for communications, interstate highways (autostrade), railways and air traffic. It is headquarters for prestigious shows, demonstrations and reviews, collectively as the Fiera Camponiara. The most renowned gothic monument is "Il Duomo." Construction began in 1386 and was completed in the XIX century. It is surmounted by innumerable spires (the highest is 108.50 meters tall) and is adorned with 3,159 statues. Other significant sacred buildings are: the V century basilica of San Lorenzo, the X-XII century basilica of Sant Ambrogio, the church of Sant Eustorgio (with the 15th century Portinari chapel), the Renaissance church of the Madonna delle Grazie (with DaVinci's original Last Supper) and the church of San Satiro, San Nazzaro and Santo Celso. Among the civil buildings the premier is the Sforzesco Castle (1368), where headquarters of the Civil Museums containing major art works is located. Other notable collections are located near the Brera gallery, the Poldi-Pezzoli museum, the Ambrosian Library and Gallery and the Gallery of modern art. The city of Milan enumerates the Museum of Science and Technology, the Museum of Natural History, and the Theatre Museum hosted by the celebrated La Scala Opera House (XVIII century). Headquarters of  the State University of Studies, the Polytechnic, the Catholic University of the Sacred Heart, and the L. Bocconi Commercial University are also located within the city of Milan.