Yellowstone: geysers, bison and springs of every colour
The world's first national park, sitting on a volcano: geysers, multicoloured hot springs, a yellow canyon and bison in the middle of the road.
Grand Teton: sheer peaks above the lakes and the plain
A range of jagged peaks rising abruptly above a flat valley, with glacial lakes at its feet. Yellowstone's neighbour, smaller and more alpine.