An inventory is presented of the flora and fauna of an urban waste-land that had laid fallow during 14 months. The plants, gastropods, spiders, insects, isopods, centipedes and millipedes of this area, the Rijndam site, were sampled on 8 May 1993. Several rare or threatened species were encountered: the plant Atropa bella-donna, the aquatic beetle Coelambus nigrolineatus, the slug Milax (Tandonia) sowerbyi, and the centipede Chaetechelyne vesuviana. These taxa, and the biological diversity of the site, suggest that urban waste-lands may play an important role in urban biodiversity. More study is needed as so far little is known of the urban ecosystem in The Netherlands.