Italy has 49 UNESCO world heritage sites (as of 2013) with 18 in northern Italy and one that includes monuments throughout Italy, Longobards in Italy - Places of the Power. Northern Italy's world heritage sites include city centers, archaeological sites, and natural sites. Sites are listed in the order in which they were inscribed by UNESCO, starting with Italy's first world heritage site in 1979, the rock drawings of Valcamonica.
The prehistoric petroglyphs of the Valcamonica was Italy's first UNESCO World Heritage site, designated in 1979. La Valle Delle Incisioni, the Valley of Engravings, is the largest collection of prehistoric rock carvings in Europe with more than 140,000 petroglyphs done over a period of 8,000 years. In addition to prehistoric sites, the beautiful Valcamonica is dotted with picturesque medieval villages and has many hiking trails.
The Convent of Santa Maria della Grazie with Leonardo da Vinci's famous Last Supper painting is a top sight in Milan. If you're going be sure to book tickets ahead (see link above for visiting information). Both the convent and the painting are from the 15th century.
Venice is one of Italy's most popular and romantic cites. Built on 118 islands, the city of Venice was chosen as an architectural masterpiece with many important works of art. The Doge's Palace is the most impressive building in Venice and Basilica San Marco is not to be missed but you'll find interesting architecture in all parts of Venice.
Ferrara, on the Po Delta in Emilia Romagna, is a walled Renaissance city with lots of great examples of Romanesque and Gothic architecture. A medieval castle dominates the old town and its 12th century cathedral is a good example of Romanesque and Gothic architecture. During the Renaissance, Ferrara was an intellectual and artistic center, designed according to the late fifteenth century principles of the "ideal city". Ferrara holds it Palio contest May and one weekend is devoted to flag throwing Stay near the castle at Hotel Annunziata.
Ravenna, also known as the city of mosaics, offers the visitor a unique look at religious mosaic arts from the 5th and 6th centuries. Eight of Ravenna's monuments and churches from the 5th-6th centuries are designated UNESCO World Heritage Sites, most because of their spectacular early Christian mosaics. During this period, Ravenna was the western capital of the Roman Empire and of the Byzantine Empire in Europe.
Modena's 12th century Duomo or Cathedral and Gothic bell tower, Torre della Ghirlandina, are in the historic center in Piazza Grande. These three monuments make up Modena's world heritage site. The cathedral is one of the best Romanesque churches in Europe. Modena is also the home of Luciano Pavorotti, balsamic vinegar, and exotic car makers like Maserati and Ferrari, who just opened the Enzo Ferrari House Museum in Modena.
Portovenere and the Cinque Terre are picturesque villages on the coast near La Spezia. Portovenere, on the Gulf of Poets, has a harbor lined with brightly colored houses and narrow medieval streets leading up the hill from the ancient city gate to a castle. Cinque Terre, five lands, are five car-free villages connected by hiking trails, trains, and ferries.