As all have said, it's strenuous. No switchbacks, just up. Straight up the mountain. In my opinion, all worthwhile hikes should have a reward at the end, and this one is well worth it: a dip in a beautiful, isolated, emerald green lake. Not every day you get to swim in a volcano. We were the first up (left just after 8 a.m.) and thus had the lake completely to ourselves. It was surreal. Also, great views on the way up prior to entering the forest. Figure 3 1/2 hours round-trip.
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