The Italian region of Umbria is enclosed between Tuscany to the west and north-west, Marche to the east and north-east and Lazio to the south; it is the only Italian region having neither a coastline nor a border with other countries. It includes the Lake Trasimeno, Marmore's Falls, and is crossed by the River Tiber. Umbria is known for its landscapes, traditions, history, culinary delights, artistic legacy, and influence on culture. Morphologically, the region is characterized by hills, mountains, and valleys. Umbria is also well known for its historical towns such as Perugia, which is the capital of the region and an important university centre of national and international fame. In addition to Perugia and Terni, Among the main centers there are Assisi, (a World Heritage Site associated with St. Francis of Assisi), Gubbio, Spoleto, Orvieto, Todi, Città di Castello, Foligno, Narni and Orvieto, which stands on a cliff overlooking the valley of the river Paglia. The region is entirely crossed, for about 200 km, by the famous river Tiber and then continues its course in Lazio. One of the largest tributaries of the Tiber, the Velino, forms the Cascata delle Marmore: an impressive a man-made waterfall created by the ancient Romans, which reaches a total height of 165 m (541 feet), making it the tallest man-made waterfall in the world. The tertiary sector is essentially based on tourism.