Ghiberti so impressed the guild with his work on the north doors that he was awarded the commission of the east doors pictured here, which took another 27 years to complete. For this set of portals, Ghiberti used “rilievo schiacciato” (meaning “flattened relief”) — a method invented by Donatello — to create incredible 3-D compositions depicting Old Testament stories. Michelangelo himself was so impressed with Ghiberti’s work that he nicknamed the doors the “Gates of Paradise.”