In Rome, at the end of May, thousands of bicyclists coming from all over the world will meet and cycle together. For the fifth year now, from May 30th to June 2nd, the Critical Mass will be "Interplanetary", the so-called "Ciemmona" (big CM). The city will be invaded by the colours, the sounds, and the bells of the most cheerful and critical event of urban bicyclists coming from all over the world.

Critical Mass is an international event which takes place in more than 400 cities around the world, each last Friday of each month, when cyclists, spontaneously and in massive way, go riding through the streets of their city, usually busy with cars.