The Papal Basilica of St. Francis of Assisi is the mother church of the Roman Catholic Order of Friars Minor, commonly known as the Franciscan Order. Burial place of St. Francis, the basilica is one of the most important places of Christian pilgrimage in Italy and pilgrims come from all over the world to visit. The basilica, which was begun in 1228, is built into the side of a hill and comprises two churches known as the Upper Church and the Lower Church, and a crypt where the remains of the saint are interred. With its accompanying friary, the basilica is a distinctive landmark to those approaching Assisi. It is a UNESCO World Heritage Site since 2000.The interior of the Upper Church is important as an early example of the Gothic style in Italy. The Upper and Lower Churches are decorated with frescoes by numerous late medieval painters from the Roman and Tuscan schools, and include works by Cimabue, Giotto, Simone Martini, Pietro Lorenzetti and possibly Pietro Cavallini. The range and quality of the works gives the basilica a unique importance in demonstrating the development of Italian art of this period.