Summits on the Air is a program where you hike to the top of a mountain an 'activate' it by making contacts from the summit. 'Chasers' then try and contact you to earn points. It is the ultimate challenge in ham radio in that you must haul all of your equipment to the top of the peak and that can involve some effort.
I can be seen here operating from the top of an unnamed 13,000 foot peak in Colorado above my cabin. The peaks in the background are over 14,000 feet tall.