Windows

A little more on Arches.  The park encompasses 119 square miles, and is endowed with more than 2,000 recognized arches, like the ones above, called "Windows."  This is the largest concentration of arches on the planet.  Made mostly of Entrada Sandstone, and the result of water erosion for the most part, they are believed to have been created in the last million years.  Since 1929 forty two of them in the park have collapsed.