Another point of reference is the Keyhole satellites (e.g., http://en.wikipedia.org/wiki/National_Reconnaissance_Office#Spacecraft http://en.wikipedia.org/wiki/

Another point of reference is the Keyhole satellites (e.g., http://en.wikipedia.org/wiki/National_Reconnaissance_Office#Spacecraft http://en.wikipedia.org/wiki/National_Reconnaissance_Office#...), which turned out to be larger than most people imagined.