Yosemite Valley may have the famous sites - Half Dome, El Capitan, and of course the waterfalls. But it also has the tourist hordes and the intense heat. It shouldn't be missed but once you've been and seen, head out of the valley and then north-east toward Tuolumne Meadows. About an hour's drive through the spectacular Sierra Nevada scenery, the road skims the shores of Lake Tenaya. Instead of passing it by like the majority of the park's visitors, park your car and get out. The clear mountain air and almost complete absence of sound or other human presence, makes this remote, crystalline lake a supremely tranquil location. I visited in late summer, when the valley was suffocating in 100-degree heat, but Lake Tenaya, at a considerably higher altitude, was pleasantly warm, and it's shallow waters cool but not freezing. Standing waist-deep in its waters, surrounded by white-sand beaches, pine forests and silver mountains, I could not imagine anywhere closer to paradise.
Yosemite National Park, ask at the visitor centre for a map and/or directions.