The distance these cover and the depth they tunnel into mountains is part of what makes them incredible, in case the description of underground aquaducts doesn't sound cool enough.
True! :) I first learnt of them years back on TV - think it was a Channel 4 (UK broadcast channel) documentary, in which they sent a British academic into somewhat hazardous situations. He walked underground along one of these tunnels. Haven't been able to find the documentary since, unfortunately.
Other ancient cities in Jordan had tunnels (https://en.wikipedia.org/wiki/Gadara_Aqueduct). These tunnels, which are thought to be originally from Iran but adopted by many cultures including the Romans, exist all over the world including in Luxembourg.