The Romans are famed for their impressive architecture. Some examples being the Colosseum and the Pantheon. Which structure built in Europe after the fall of the West Roman empire was too technologically advanced for the Romans to have been capable of building it themselves?

by sexy_gunther

I'm not referring to a specific building material which may not have been available to the ancients, but more to structures using a more modern construction process or technique to allow a larger, more complex building.

Follow up questions: why would they have found difficulty in building it?

Edit: I'm referring to the FIRST structure built after the fall of the empire, apologies.

kitchensink108

This subreddit isn't a huge fan of 'first/lasts" questions, so just in case this runs afoul of the guidelines, here's an alternative question:

Did post-Rome European construction technology immediately surpass that of the Western Roman Empire, and if not, when did it finally reach that point?