Some of the tallest ancient American ruins continue to inspire awe and curiosity.

The unusual burial monument of Arizona's first governor.

Once a year, at exactly 11:11 a.m., this monument comes to life.

This Arizona observatory is famous for investigations into Martian life, and as the place humans first spotted Pluto.

A replica of the flagpole that gave a frontier town its name.

Ancient pueblos built into the base of a natural canyon wall.

The unusual patterns in this rock formation result from two distinct modes of weathering.

A tunnel with windows, so you don't miss out on the impressive views.

This isolated outpost was once the only place to cross the Colorado River for hundreds of miles.

Most-visited and most-photographed slot canyon in the American Southwest.

Dramatic river bend surrounds a natural red-rocked pedestal.