The paper presents an integration platform for space-based interoperability among heterogeneous components in open smart spaces. The key idea is to rely on multiple spaces, be they physical or logical, and on mappings among spaces. Components publish their information on one or more spatial publication contexts, whereas they make subscriptions to one or more spatial subscription contexts. Information is delivered whenever a non-empty intersection among publication and subscription contexts is recognized according to the space mappings. The platform defines basic space models that can be specialized to model domain-specific spaces. The paper presents the basic platform mechanisms and their application in a sample scenario, discusses the benefits of the approach and compares it to significant related works.