The "Pont del Diable" in Tarragona is a Roman aqueduct contructed around the time of Augustus (27 BC - 14 AD, for those of you keeping score) just north of the city of Tarragona (about 100km SW of Barcelona). They've done a marvelous job restoring the aqueduct and you can even walk across it. I highly recommend visiting on a Thursday afternoon in late January - the weather was fantastic and Danielle and I were the only ones there! https://en.wikipedia.org/wiki/Les_Ferreres_Aqueduct
Just a 2000-year-old Roman viaduct. Nothing special in this part of the world. Mind-blowing for someone like me from the so-called new world.