In the page's words:

Critical Mass is an open, regular bike ride where people ride through the city together to create visibility for cycling. It is about safe, liveable streets, consideration and having fun riding together - without registration, for all age groups.

Critical Mass Bonn
In Bonn, we usually meet on the last Friday of the month at 18:00 at the Hofgarten. We ride through the city as a relaxed group, show our support for bicycle-friendly infrastructure and get into conversation. Anyone can join us - a leisurely pace, a friendly atmosphere, Bonn belongs to the bike for a ride.