The advent of the Internet has led to dramatic changes in the cultural habits of citizens, the most remarkable of which is undoubtedly the democratization of the access to the culture. Focusing in the museum world, we foresee a new generation of information systems providing compatibility with the sensorial richness of existing in-place visits, augmentation of visits with virtual information so that artworks are better understood, dynamic content management, and ubiquity. In this paper we introduce the notion of Hybrid Museum as a virtual organization consisting of a physical museum where visitors are present, plus a distributed heterogeneous collection of sources of catalogued artwork, a middleware infrastructure to provide ubiquitous access to those sources and a wireless infrastructure so that disseminations may be available to visitors at any moment. We aim at building hybrid museums by integrating heterogeneous distributed sources that are managed and operated independently. We identify the different services hybrid museums must provide, and use the grid architectural model which has been successfully tested in other virtual organizations, to define their architectural features. Finally, we also describe MoMo, an implementation of a hybrid museum running on market-based handheld PCs to prove the feasibility of our ideas.