A spatial query language, useful to querying spatial databases and retrieving spatial information, becomes efficient, effective and pleasant-to-use only if its surrounding environment is able to provide unskilled users with immediate and comprehensive access to the supplied visual operations. In this paper we describe how a usability evaluation process has been applied to improve the interface of the visual environment WebMGISQL 3D, a web application for querying and retrieving spatial information, with special focus on those phenomena where the third dimension is a relevant feature.