Crater lake is such a beautiful National park, the highlight is definitely during sunset time with the amazing colors of the sky reflecting on the lake! Here is a cool hike to do while over there: Garfield peak trail. It is a 3.3 miles trail south of the park that is leading you to a really cool view of the lake. It is a bit steep with 1000 ft elevation but gives you at some point a great view of the lake at 8000 ft elevation.
My only big advice would be: Take mosquito repellent with you... it was during summer and we have been attacked all day.
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