Yellowstone

Whoever labeled Yellowstone "a park" made a grave error: the size of it is mind-boggling and exceeds two or three european states put together. Just to make the recommended one-day tour took us 10 hours - we climbed steep mountains, crossed The Continental Divide twice at more than 6000 feet, crossed vast valleys churning with geisers and watched elk, bison and moose.
The most impressive was the Norris valley of geisers. There one can walk past the Porcelain Lake, admire multicolored hot holes...
I dipped my hand into a warm stream and smelled a slight odor of sulfur. Dead trees stood on the whitened ground...
The Yellowstone lake was equally impressive - seemingly endless, it is also fed by geisers - some of the holes are under the water and look like tiny volcanos...
We also watched the eruption of The Old Faithful!