Vatican Spiral Stairs on Flickr.
The Vatican Museums spiral staircase is one of the most photographed in the world, and certainly one of the most beautiful. Designed by Giuseppe Momo in 1932, the broad steps are somewhere between a ramp and a staircase. The stairs are actually two separate helixes, one leading up and the other leading down, that twist together in a double helix formation. Little did the Vatican Museum know in 1932 that this formation would come to represent life itself, with the discovery of the double helical DNA strand.