The Library of Congress has done terrific work putting on line parts of its vast photograph collection.  For a sample of those taken by the scientist and documentary photographer
Sergei Mikhailovich Prokudin-Gorskii (1863-1944) in the old Russian Empire between ca. 1905 and 1915, in astonishing color, go here (the comments are great, too!); the complete set is at the Library of Congress site, here.