We analyse the geographic proximity of innovative firms to different types of knowledge sources in an urban environment on a microgeographic scale. Based on a comprehensive panel data set of manufacturing and service firms in the German capital city Berlin, we investigate the characteristics of firms' knowledge environment while differentiating by the type of innovation. Geocoded firm locations at the level of individual addresses allows us to describe the knowledge environment of firms on a very fine microgeographic scale. We find that innovative firms are located in places with higher numbers of same-sector firms, more start-ups and a higher inflow of other firms. They also locate in closer proximity to universities and research institutes. These differences decay rapidly within a few metres (50-250 m), indicating a truly microgeographic scope of knowledge sources in urban environments.