Bandelier National Monument, New Mexico protects Ancestral Pueblo archeological sites and a diverse and scenic landscape. Much of the area was covered with volcanic ash (the Bandelier Tuff) from an eruption of the Valles Caldera volcano 1.14 million years ago. Ancestral Puebloans broke up the firmer materials to use as bricks, while they carved out dwellings from the softer material. (source: Wikipedia) I was also intrigued by the natural carvings from wind and weather and with a little fantasy you can find interesting sculptures, like this tree shape, in the walls of Cañon de los Frijoles.