I live in the Eifel. This is a low mountain range in western Germany and eastern Belgium. We have some volcanic lakes here and one of the well known is the Lake Laach. It's a nice lake with very beautiful parts of a nice hiking trail direct on the shore. And I'm often fascinated that there is still volcano activity which you see and smell. On some places you have an intensive Sulfur odor and many bubbles on the surface of the lake. On the second picture here you can see such a bubble field on the shore. There is so much activity that you expect a massive volcano eruption but nothing happen. It's more like a meditative nature show which smells like old feet. I hope you can smell it.
Photographic are there two areas here. Once the shore where you can walk and make picnic near the water and on the other side of the lake a strict nature reserve so you can't reach the shore. Here is an extensive bird population and something like a dense jungle. There is also the Maria Laach Abbey which has an absolute fantastic library where I hope to make someday photos in there. All in all is there a nice trip target with many beautiful spots.