Wow, this was quite a pice of work! Okay, here’s what I did.

First I developed two versions of the picture, one in color and one in b&w. For the b&w version, I adjusted the colours so the sky would be darker and much more dramatic, also the greens would be a bit darker and the yellows and oranges brighter for more contrast. I then exported both as 16 bit TIFFs and loaded them into Paint.NET, where I merged them. Regretfully, after merging the sky wouldn’t be as contrasty as I had hoped, so I meticulously seperated it from the fore- and background using the magic wand. Then, I seperately adjusted the tone curves for the sky and for the rest of the image, so that I got this as a result.

"Relax" | Olympus E-P1 + Lumix 20/1.7 @ f/8, 1/250 sec, ISO 200

This would probably have been a lot easier with Photoshop …