This paper describes an experiment to elicit referring expressions from human subjects for research in natural language generation and related fields, and preliminary results of a computational model for the generation of these expressions. Unlike existing resources of this kind, the resulting data set - the Zoom corpus of natural language descriptions of map locations - takes into account a domain that is significantly closer to real-world applications than what has been considered in previous work, and addresses more complex situations of reference, including contexts with different levels of detail, and instances of singular and plural reference produced by speakers of Spanish and Portuguese.