Abstract: This paper presents an approach to designing a spatial query language called GeoSQL, by extending the standard database language SQL. A critical factor to the design is how to accommodate spatial operators in an appropriate structure, while conforming well to the basic principles of SQL. To achieve this, the FROM clause of SQL is restructured to contain spatial operators via a subquery so that the results of spatial operations can be easily fed into both the SELECT and WHERE clauses. This is a distinct characteristic of GeoSQL. The syntax and semantics of GeoSQL are described, and a set of examples for testing the expressiveness of the language are given. The interface of the language is also designed with the introduction of visual constructs (e.g., icons and ListBoxes) to aid the entry of query text. This distinguishes GeoSQL's interface from the previous extended SQLs, which formulate a query only by typing. An implementation of GeoSQL is also discussed.