Hi @shaka how are you ?. I am glad that you bring us part 4 of this wonderful adventure of yours by Jura of Swabia, this time by the beautiful lakes of Blautopf. To be honest I had never heard or seen this place, but let me tell you that it is a super beautiful place, They love the pictures because you can clearly see the beauty and splendor of this fantastic place. I am very surprised that Hasenmayer found the first cave full of air after a 1250 m long dive behind the Blautopf, that means it is an excellent discovery and his name right now is a relic. The highlight of Blaubeuren, it is worth a visit. Pretty blue and green lake. It feels like a leftover piece of the Middle Ages, in addition to having beautiful views. It is a natural enclave with a beautiful lake and I was able to investigate and read what I could do to take a relaxing walk and spend some pleasant hours. Of course, it takes no more than two hours to visit the town and the lake. And with regard to your question about the blue water, I think it's because of the weather and the flow, it's the result of the physical properties of a limestone densely distributed in the water pipe, plus the sunlight contributes to accentuate the color of water I hope this something successful in the answer and good thanks for other fantastic and beautiful pictures. Greetings from Venezuela.