This workshop promotes ubiquitous computing research in authentic urban setting, with real users and with sufficient scale and time span. We first motivate why such research is important and then describe our ongoing deployment of diverse computing resources in a city center to support such research. We are organizing an UBI Challenge, to make our urban computing testbed available to the international research community and to stimulate research collaboration in a very concrete manner. This workshop calls together researchers on real world urban computing to prototype applications and services that could be realized atop such computing resources. Author Keywords Ubiquitous computing, urban computing. ACM Classification Keywords K.4.0 [Computers and Society]: General. General Terms Experimentation, Human factors, Verification. MOTIVATION Since Mark Weiser coined the term “ubiquitous computing” in the 1980’s [12], we have seen an immense research investment in ubiquitous (or perva...