HOW TO BUILD A CATHEDRAL (Into the Medieval Mind). The great cathedrals were engineering marvels of the medieval world built with not much more than pulleys and ropes, chisels and hammers and set squares. Architectural historian Jon Cannon searches for answers on how these structures were built and the ambition that it took when looking at Glouchester, York, Norwich and Ely. ©BBC

http://youtu.be/5u9rjssGJrc

SALISBURY CATHEDRAL (ENGLAND)