This paper presents CityMockUp, our contribution to the CHI'15 student design competition. CityMockUp emphasizes and proposes a solution to the problem of involving citizens in the actual process of furnishing or shaping the urban environment that they inhabit. The design consists of digitally interconnected and tangible wooden modules that enable the citizens to construct their own desired urban architecture proposals. The product is rooted within and contributes to the emerging field of Urban Interaction Design (UIxD).