Funny. Growing up near there, and often passing by I just thought 'what a mess'. Because it's made out of soft stones which erode easily, and thus large parts of it are always encrusted in scaffolding for repairs. And when they are ready with that part, they can move the scaffolding to the next part, and start all over again. Without pause. They still believe. I believed in taking it as a shortcut from main station to shopping street during rain :)
It also gave my hometown 'interesting' acoustics, because of this:
I'm sure they used the soft stones because they were easier to carve. But I'm surprised someone in the modern age hasn't come up with a way to treat porous stone like this to make it more weather-resistant, so they don't have to do so much maintenance and repair on these old stone structures. It would be similar to how we use treatments in dentistry to fill the pores in teeth and make them less sensitive and wear longer.
I think that's because of "Denkmalschutz", which means not changing the 'character' of the building, down to not really changing the building materials, even if they wouldn't look different from the outside.
It also gave my hometown 'interesting' acoustics, because of this:
https://de.wikipedia.org/wiki/Ennert#/media/Datei:Bad_Godesb... & https://de.wikipedia.org/wiki/Rabenlay which reflected the sounds of ships on the Rhine, trains on both sides of it, right to where this picture was taken, and a little bit behind. All the times.
Why? Because they took the stones from there. And from all around it. But the Romans did it first.
Ejal. Kölle Alaaf! Schweinheim Wutz, Wutz! (Carnival thing, doesn't really matter)