Location information 5 Categories Next ride Date:  ? (noch festzulegen) Time:  ? (noch festzulegen) Location:  ? (noch festzulegen) Photos CriticalMass.at History 2009 While having a Critical Mass on the last Friday of every month, Graz rode its 22nd 'CM' event on 26 June 2009 as its first World Naked Bike Ride. Argus