Hetch Hetchy - Yosemite - National Park Service Hidden in Yosemite National Park’s peaceful northwest corner, Hetch Hetchy Valley is a treasure worth visiting in all seasons. Located at 3,900 feet, Hetch Hetchy boasts one of the longest hiking seasons in the park and is an ideal place for thundering spring waterfalls and wildflower displays. High temperatures prevail in summer months, but that is a small price to pay for the reward of vast wilderness filled with stunning peaks, hidden canyons, and remote lakes.