We introduce Spatial Tuples, an extension of the basic tuple-based model for distributed multi-agent system coordination where i) tuples are conceptually placed in the physical world and possibly move, ii) the behaviour of coordination primitives may depend on the spatial properties of the coordinating agents, and iii) the tuple space can be conceived as a virtual layer augmenting physical reality. Motivated by the needs of mobile augmented-reality applications, Spatial Tuples explicitly aims at supporting space-aware and space-based coordination in agent-based pervasive computing scenarios.