I fondly remember spending hours and hours in the T-Online BTX, which looked something like this: https://www.spiegel.de/fotostrecke/btx-jubilaeum-so-sah-der-internet-vorlaeufer-aus-fotostrecke-34503.html
There was this chat "village" themed based around Asterix & Obelix. I think it was the first chat I ever used, so it was magical. My older sister would mostly chat, while I watched. I still remember her handle from back then: Gutemine.
We later found out the chat cost 5ct/min (or 5 Pfennig per minute?)