Ok but no one else was running water through their city like that! One thing to have the idea, another to say yep not only will we run the water, we'll do it close enough to walls so that they're cooler
Discussion
Not just Romans, many ancient civilisations used water and underground chambers for refrigeration. It's amazing how much we've forgotten with the ease of use of electricity.
https://en.m.wikipedia.org/wiki/Yakhch%C4%81l
https://www.ancient-origins.net/artifacts-ancient-technology/ancient-advanced-technology-021700