Ancient Roman Water Systems from 2000 Years Ago

I saw in a documentary that it's still usable today. I wonder what would have happened if Rome hadn't fallen; their technology was incredible. 2,000 years ago, the Romans brought spring water from 86km away to the city without a single pump. The secret was a barely noticeable gradient, dropping only 1 meter for every kilometer. But things got complicated when a deep gorge appeared right in the middle of the path. Initially, they built a 50-meter high structure of stacked stone arches and placed the water channel on top. That's the famous Pont du Gard. The problem was a gorge over 100 meters deep. Building a bridge that high was simply impossible in terms of cost and time. So, the Romans flipped the concept: they confined the water in lead pipes, plunged it down to the bottom of the gorge, and then pushed it back up the opposite slope. If the destination tank was even slightly lower than the starting tank, the water would naturally find its own level and rise. The aqueducts of Lyon crossed a 120-meter deep gorge using this method with nine pipes.