A tree data structure, similar to a B-tree, used for indexing spatial data within a database. In an R-tree structure, data is sorted into a set of hierarchical nodes that may overlap. Each node has a variable number of entries, each of which includes an identifier for child nodes or actual data elements and a bounding box for all entries within the child node or the data elements. Searching algorithms check the bounding boxes before searching within a child node, thus avoiding extensive searches.