One day hike that hasn't been recommended that I would definiately put high on the list would be Young Lakes... You have to make sure you hit the upper lake, though. This hike gives some incredible views of Yosemite's north with all of its rugged beauty. If you don't enter the park over Tioga Pass one of these hikes out of Tuolomne Meadows is a must. Actually... A hike out of Tuolomne Meadows area is a must anyway.
I'll have to admit, though... Half Dome, even with all the people you'll meet in one day, is one of those hikes you'll never come close to mirroring anywhere else. The view from the top is incredible and hauling your a$$ up those cables is something you'll never forget.
I guess what I'm trying to say is... 3 day hikes in Yosemite??? Where do you start??? Just make sure you do at least one trip in the northern part of the park along Hwy 120, or for my money, you'll have missed most of its beauty.
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