Stinky water, well hidden in the Mikulůvec forests

Grandma called the place "smelling water". I say I have to go from Kateřinské pasek down through the forest towards Mikulůvka and there I will find it "by smell". Mudflats that smell like rotten eggs.
I tried it several times. But the forests above Mikulůvka are deep and confusing, I didn't succeed. I tried again from time to time with the same result. Only recently did I receive the news that there is a new...