Today's disruptive approaches to rearchitecting the Internet, e.g., Clean Slate Networking initiatives require testbeds that present unprecedented flexibility to the experimenter. This poster presents Berlin, a flexible testbed platform designed towards the requirements of Future Internet research. Berlin combines a diverse landscape of network elements, both software-defined and legacy hardware, and unifies them under a common management interface, presenting them as pluggable services to the experimenter. Key words: future internet, testbed support, experiment services