Since 2008, !Mediengruppe Bitnik has been conducting walks through the sceneries of invisible cities: Equiped with self-built CCTV video signal receivers and video recording devices they organise Dérives in search of hidden - and usually invisible - surveillance camera signals in public space. Surveillance becomes sousvellance: The self-built tools provide access to „surveillance from above“ by capturing and displaying CCTV signals, thus making them visible and recordable.