The European Model for Inhabited Areas (ERMIN) was developed to explore recovery optionsfollowing the contamination of an urban environment with radioactive material. This paperdiscusses the user experience of ERMIN and in particular it concentrates on thedevelopment of a description of the urban environment and how that description affects theoutput. The user interacts with ERMIN by defining different regions on a map. A region maybe an area in which a particular combination of recovery countermeasures is applied, orwhere a particular level of contamination is found, or where there is a particular type ofurban environment. Most of the output from ERMIN is also presented as maps with summaryinformation that allows the user to compare different countermeasure strategies. ERMIN hasbeen implemented within two international nuclear accident Decision Support Systems; RODOSand ARGOS. Both systems have user interfaces that exploit geographic information system(GIS) technology which complement the ERMIN map based approach.