Have you ever wondered what it would be like to take a historic tour of the Colorado River Canyon? Wonder no more, as this site from the U.S. Geological Survey makes just such a sojourn possible. Drawing on thousands of historic and contemporary photographs, views, documents, and other items, the USGS has created these fine 3D and photographic tours of dozens of national parks. On the site, visitors will find an alphabetical list of the parks, along with links to the 3D image galleries, standard image galleries, and selected online field guides. There's a great deal to recommend here, but visitors should definitely look at the stereograph images from the Powell Survey Expeditions of the Colorado River from 1871 and 1872 (in the "Other park-related resources" section) and the guidebook titled "Where's the San Andreas Fault?" Along with providing entertaining edification, this site might also spark some ideas for an upcoming trip.