In a TED interview, Elon Musk stated:
People are mistaken when they think that technology just automatically improves. It does not automatically improve. It only improves if a lot of people work very hard to make it better, and actually it will, I think, by itself degrade, actually. You look at great civilizations like Ancient Egypt, and they were able to make the pyramids, and they forgot how to do that. And then the Romans, they built these incredible aqueducts. They forgot how to do it.
It makes sense that if people stop focusing on some goal, the knowledge of how it is achieved will become lost or at least uncommon. And the ancient Egyptians did stop building pyramids at some point; given the speculation about construction techniques, it's fair to say that those methods were lost after a certain time. My question is about the Roman aqueducts. The Wikipedia article on this topic says:
During the Renaissance, the standing remains of the city's massive masonry aqueducts inspired architects, engineers and their patrons; Pope Nicholas V renovated the main channels of the Roman Aqua Virgo in 1453. Many aqueducts in Rome's former empire were kept in good repair. The 15th-century rebuilding of an aqueduct at Segovia in Spain shows advances on the Pont du Gard by using fewer arches of greater height, and so greater economy in its use of the raw materials. The skill in building aqueducts was not lost, especially of the smaller, more modest channels used to supply water wheels.
Was the knowledge of how aqueducts were made actually lost at some point in that part of the world? I'm not sure if it was lost and then reinvented during the Renaissance, or if there was continuity in the passing of the knowledge.