The attraction in Ronda is a Roman road that spans the gorge that splits Ronda in two crosswise.

It's likely that the viaduct was just a means of getting some legion from point A to point B, and that Ronda was simply in the way.

Like much of what's called 'The Spanish Hill Country', Ronda is built on rough terrain.  Houses cling to the cliff face like moss, and no spot is too precipitous that it can't serve a purpose.  There is a hotspot almost dead-center in this image.  Click it.