The magnificent Basilica di San Francesco, a true treasure chest, looms over the plain on a formidable basament. It dates from the thirteenth century and was built shortly after the death of the saint. From the square, surrounded by fifteenth-century porticoes, we enter the Chiesa Inferiore, or lower church, through a fine portal. The remains of Saint Francis are held here. The Chiesa Superiore, or upper church, one of the finest examples of Italian Gothic, is large and luminous and preserves the famous fresco of the Life of Saint Francis by Giotto, considered a key work for the rebirth of western art after the dark centuries of the Early Middle Ages.