The 120 km Rwenzori Mountain chain has also been referred to as the "Mountains of the Moon", originally labelled such by Ptolemy in A.D.150. Reaching an elevation of 5,109 meters, it is Africa's 3rd tallest mountain range, exceeded in altitude only by the free standing Mt. Kenya and Mt. Kilimanjaro. The distinctive glacial peaks are visible for miles around, but the slopes above 1,600 meters are the preserve of hikers, who rate the Renzoris to be the most challenging of all African mountains. A variety of large mammals inhabits the lower slopes, but the Rwenzoris are more notable for their majestic scenery and unusual vegetation. The trails lead through rain forests full of monkeys and birds then on to tall bamboo forests, before emerging on the high altitude moorland zone, a landscape of bizarre giant lobelias, towered over by black rock and white snowy peaks. The activities offered in the Rwenzoris include a 6-day loop trail, which is a tough but rewarding hike, taking in all the vegetation zones, with the exception of the glacial peaks. Shorter, more popular hikes can be arranged as well. The high peaks should be attempted only by experienced mountaineers as they can be extremely challenging.