I've been looking back at some of the pictures from Yellowstone over the past couple of weeks. I seem to be missing a large number; Mr Z assures me they are on a computer somewhere, but who knows where? I guess that means we will have to go back.
There were some beautiful colours in the hot pools there. Here are a couple of the Black Pool - it had some cyanobacteria in it for a while that turned the water very dark, but it's been back to its gorgeous aqua self for over 20 years now. Apparently.