Les Portes du Soleil (literally “The Doors of the Sun”) is a major skisports destination in the Alps, encompassing thirteen resorts between Mont Blanc in France and Lake Geneva in Switzerland. With more than 650 km of marked pistes (claimed by the lift companies; an independent expert measured about 426 km and about 200 lifts in total, spread over 14 valleys and about 1,036 square kilometres (400 sq mi), Portes du Soleil ranks among the two largest ski areas in the world (the other being Les Trois Vallées). Almost all of the pistes are connected by lifts – a few marginal towns can be reached only by the free bus services in the area. The highest point of skiing is 2400 m and the lowest is 900 m. As with many other Alpine ski resorts, the lower slopes of the Portes du Soleil have snow-making facilities to extend the skiable season by keeping the lower slopes open during the warmer months.