I've driven over or by the Hoover Dam countless times. These pictures give a really good glimpse into its construction. I have a hard time imagining how someone can think up a project this size, and actually make it happen.
The far side of the moon, illuminated by the sun, is seen as it crosses between our 'EPIC' camera on the Deep Space Climate Observatory (DSCOVR) satellite, and the Earth - one million miles away. Check it out: http://go.nasa.gov/1Dq0IOh#EarthRightNow