cf. city flows is a comparative visualization environment of urban bike mobility designed to help citizens casually analyze three bike-sharing systems in the context of a public exhibition space. Three high-resolution screens show the space of flows of New York City, Berlin, and London through visualizing the bike-sharing systems of these global cities. By showing the flow of multiple cities side by side, we can compare their extent and dynamics. Tracing urban movements accentuates different urban structures, and contrasts grid-plan cities like New York with historically grown cities such as Berlin. It also enables us to observe and dwell on similarities and differences in various bike-sharing systems. With our visualizations we want to understand the pulse of urban mobility and create portraits of a city defined by its transient dynamics. Cycling is increasingly recognized as critical component of future urban mobility. Riding a bike is largely independent of other traffic and unaffected by road congestion, and has health and environmental benefits. In the last few years, many cities around the world installed bike-sharing systems in order to stimulate casual use of bicycles by locals and visitors alike. We used data from these systems to visualize various aspects of bike-sharing mobility. cf. city flows is an installation that combines multiple visualizations of bike-sharing journeys in three cities. It applies established mapping and visualization techniques within a highly aestheticized framework in order to animate visitors to engage with urban mobility.