Volcán Puyehue, Chile: this was extreme and a pure miss (Here be Dragons!)
We actually followed an old instruction before the whole area changed by a huge erruption.
It was supposed to be an easy 4 h hike to hot springs. It took us 11 hours to get there through a devastated "moonscape" covered by a thick layer of volcanic dust.
Extremely demanding hike without water through gorges. The whole landscape changed. The errupting volcano moved a river one valley further.
We had to climb 500 m down just to get a water and overnight. And the other day we did it the same way back.
I do not share any instruction, because I do not recommend it.
Now there are probably newer guides to folow to explore the area around.