Major Powell's 1873 Expedition through the Canyons of the Colorado River

You have to look closely for the boats on the river in the lower left corner of the picture (click on picture to enlarge).  That gives you some idea of the scale of the canyons.  Interesting note:  I did this watercolor from a watercolor by an artist who was actually on the expedition, documenting what they saw.  I wondered how the artist caught up with the rest of the party as he painted them floating away from him.  Maybe they had a third boat.