This article proposes a classification for a subset of English spatial prepositions which is argued to have cross-linguistic validity by using it to classify a subset of Spanish spatial prepositions. The classification consists of a hierarchy of spatial relations where each node in the hierarchy satisfies a series of syntactic and semantic tests. These tests define properties which are then inherited uniformly throughout. Prepositions are assigned values from the lower nodes in the hierarchy either in the lexicon or through lexical rules. Similarities and differences between the spatial system of different languages can be described by appealing to the relations and lexical rules that the language allows. It is shown how the hierarchy is used for building a lexicon for the machine translation of spatial prepositions in a transfer-based system.