That is the island of Lombok in the background...Mount Rinjani, actually. Mount Rinjani is an incredible hike, but a tough one. When you get to the top, there is another volcano inside the caldera and a lake...I have not been there yet, but have seen photos...an incredible sight, and supposedly there is a unique ecosystem around the lake that only exists in that location...it is on my bucket list to climb...one of these days..
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