Mountain Madness interests. While leading Mountain Madness, Fischer became renowned for his ascents of the world's highest mountains made without the use of supplemental oxygen. Fischer and Wally Berg were the first Americans to summit Lhotse, the world's fourth highest mountain (27,940 feet / 8516 m), located next to Mount Everest. He and Ed Viesturs were the first Americans to summit K2, (28,251 feet / 8611m) in the Karakoram of Pakistan without supplemental oxygen. During his stewardship of Mountain Madness, Fischer led social and environmental initiatives to help people in the countries in which Mountain Madness traveled. As the leaders of the
Karakoram them exceeding : K2, the second highest peak in the world at , Gasherbrum I, Broad Peak and Gasherbrum II. The range is about in length, and is the most heavily glaciated part of the world outside the polar regions. The Siachen Glacier at and the Biafo Glacier at rank as the world's second and third longest glaciers outside the polar regions. The Karakoram is bounded on the east by the Aksai Chin plateau, on the northeast by the edge of the Tibetan Plateau, and on the north by the river valleys of the Yarkand and Karakash rivers beyond which