The Alps are one of the highest and most extensive mountain ranges in Europe, stretching approximately 1,200 km across eight Alpine countries: Monaco, France, Switzerland, Italy, Liechtenstein, Germany, Austria and Slovenia. The Alpine arch extends from Nice on the western Mediterranean to Trieste on the Adriatic and Vienna at the beginning of the Pannonian Basin. The mountains were formed over tens of millions of years as the African and Eurasian tectonic plates collided.