adventure alpine alpinism alps altitude backpacking brave challenge climb climber climbing cold dangerous glacier glaciology global Graubünden hiking holiday ice ice-flow icy landscape man Morteratsch mountain mountaineer mountaineering mountains nature outdoor recreation risk silhouette snow sport sports summit swiss switzerland terrain tour tourism Trek Trekking warming winter Expedition exploration extreme change cliff cliffs climate edge melt melting ridge eiffel France monument Paris tower paysage pierre provence Ruine active backpacker hike hiker outdoors outside walk walking people direction mark rock sign photographer forest path