Deutsche Bahn managed the feat of delaying my train connection already before my departure: Due to a diversion, the duration of my journey from Brussels to Frankfurt am Main was extended by an hour. So, I suddenly had a negative transfer time. Therefore, I had to leave Brussels two hours earlier. At least, this then gave me about an hour and a half to stroll through Frankfurt (despite the apparently obligatory delay).
I took full advantage of this opportunity: From the main train station, my route first took me past the Eurotower, the former headquarters of the European Central Bank. Then, I strolled into Frankfurt’s old town, to the Römerberg. This central square is full of (restored) half-timbered houses and does not give the impression of a big city at all – definitely a nice place to while away a bit of time until my connecting train.