Marble Canyon: The first section of Grand Canyon, cutting north-south through an open valley known as the Marble Platform, is sheer-walled Marble Canyon. The first sizable rapids river runners encounter, House Rock Rapids, lies at the mouth of Rider Canyon, about 17 miles downriver from Lees Ferry.

Redwall Cavern: About 33 miles downriver, the Colorado River carved this large cave from the Redwall limestone formation. Explorer John Wesley Powell, clearly impressed at its vast size, wrote that it could hold 50,000 people. Doubtful—but it is big. River runners often stop here for lunch on the beach or a game of Frisbee inside the cavern’s sandy expanse.

Nankoweap Ruin: High above the Colorado River near Nankoweap Canyon, around river mile 53, the Ancient Puebloans, also known as the Anasazi, constructed masonry granaries to protect their food stores. The steep route up to the ruins, which are about 1,000 years old, offers striking downriver views.

Little Colorado River Confluence: Just past mile 61, the Little Colorado River (LCR) joins the Colorado. The warmer turquoise waters of the LCR harbor several endangered fish species, while the cliffs shelter prospector Ben Beamer’s historic cabin.

The Inner Gorge: Past its confluence with the Little Colorado, the Colorado River swings west, entering the darker, harder rocks of the Inner Gorge (also known as Granite Gorge) carved below the Tonto Platform. This section is the heart of Grand Canyon, sometimes referred to as “the canyon within the canyon,” with rock layers 2 billion years old.

Phantom Ranch: Designed by architect Mary Colter, these stone-and-wood cabins are the only accommodations in the inner canyon. Shaded by cottonwoods, lying between Bright Angel Creek and the Colorado River, Phantom Ranch is a riparian oasis in the inner canyon’s harsh desert environment.

Deer Creek Falls: This 100-foot-high waterfall tumbles out of a sinuous Tapeats sandstone narrows on the lower river—an awe-inspiring sight and a popular spot for water play.