Hauptwache! It’s not just a smelly railway station!
Back in the days when Frankfurt was its own semi-independent Imperial city state, the Hauptwache and its partner the Konstablerwache (about five minutes walk down Zeil, Frankfurt’s main shopping street) were the centres of Frankfurt’s martial might. The army and police (not that there was any real difference in those days) worked from these buildings, and they also served as armouries. This meant that it was a target for revolutions, such as the uprising of 1833, and for enemy countries. When Prussia annexed Frankfurt, they shut down the Frankfurt army and converted Hauptwache into a jail.
These days, the Hauptwache (reconstructed after being bombed) is a pricey cafe. It’s normally surrounded by parasols, planters and benches, which make it rather hard to actually see the building. I’ve stripped these away, so you can hopefully see the lovely architecture better. And yes, there is really a suit of (carved) armour over the entrance, sitting on a pile of shields and spears – the one reminder of its time as an armoury.