La Merveille (The Marvel), Mont Saint-Michel, France — This masterpiece of early Gothic monastic architecture on the north face of the rock houses three levels of rooms — the almonry and cellar below, the Guest Hall and Knights Hall above, and the cloister and refectory at the top. Its construction required piling thousands of tonnes of stone onto the sheer granite face without modern lifting equipment.
© Jorge Láscar from Melbourne, Australia, CC BY 2.0, via Wikimedia Commons
