Medieval masterpiece - NOT amateur radio

Ely Cathedral, UK, is a masterpiece of medieval engineering.  It was built about 1000 years ago, but the central tower collapsed in 1322 and was replaced by the octagon tower we see today.   

The whole cathedral was built in a time before CAD, lorries and cranes. I still marvel at the octagon every time I see it remembering that much of the cathedral is hundreds of years older!