Concept
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Created by Boundless
Architecture of the Holy Roman Empire

Speyer Cathedral, Image by Alfred Hutter
Speyer Cathedral was built during the Romanesque era; in the 11th century, it was the largest building in the Christian world and an architectural symbol of the power of the Salian dynasty.
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"Speyer---Cathedral---South-View---(Gentry)."
http://en.wikipedia.org/wiki/File:Speyer---Cathedral---South-View---(Gentry).jpg
Wikipedia
License: Other.