text: Some long ago inventer discovered that if you place carefully shapped rocks just so they will remain in place as an arch, dramatically reducing the amount of stone you need to hold up a bridge, an aquaduct, or the entrance to a castle. It probably wasn't too much later that someone recogniced that a bunch of arches next to each other would yield an arched ceiling to a room. My guess is that it then took a very long time for someone to recognize that if you made a series of arches in a circle you could make a domed room. But as soon as one was built, I suspect that a priest of some kind looked up and immediately saw that a minature version of the sky had been created, and that an artist could transform this sky into a 'Vision of Heaven.' 
  
  This book shows what decoration has been applied to the insides of domed buildings from about the second century to the twentieth. It is an absolutely spectacular set of photographs of how artists have brought the heavens down to earth.
  