The vision of a Single Information Space in Europe for the Environment (SISE) requires seamless access to environmental resources, including data, models and services. Standardization organizations like OGC and OASIS have laid the foundations for interoperability on a syntactic level for many aspects of distributed environmental information systems (e.g. OGC SWE for sensor information). At the same time, the EC has undertaken a considerable effort to commit European stakeholders to offering their environmental information in such a way that it is accessible by interested parties, both on the scientific level by supporting research projects, like ORCHESTRA and SANY, and on the legal level by introducing directives (such as the INSPIRE directive). This development, amongst others, has led to the present situation in which a large number of environmental information sources are available. However, to implement the vision of the SISE it is not enough to publish resources. Environmental information must be discoverable, and it must be ‘understandable’ in different contexts in order to be used effectively by parties of various thematic domains. Therefore, in order to foster the implementation of SISE, semantic interoperability is a necessary element. Key to semantic interoperability is the presence of meta-information which describes the concepts of the environmental resources. Producing this meta-information puts a heavy technological burden on the individual resource providers such that it seems unlikely that enough semantic meta-information will ever be made available to reach semantic interoperability and thus accomplish the vision of SISE unless other ways to provide this essential meta-information are found. In this paper we introduce an architecture, developed in the FP7 project TaToo (247893), which tries to overcome the aforementioned obstacles by providing the possibility to easily annotate and rate environmental information resources, even by parties which do not own the resource, and transparently equipping this information with domain knowledge and thus enhancing discoverability and usability of resources with semantic technologies. The objective of the architecture is to seamlessly blend in with existing infrastructures by making use of de facto standards while offering support for discovery, annotation and validation of environmental resources through open interfaces.