To facilitate comparability of our metaphor annotations across barriers of languages and cultural traditions, the CRC is developing a conceptual thesaurus (CT) as a shared reference system. Its taxonomy is based on the Historical Thesaurus of English (Kay, 2009), albeit extending and adapting it for the languages and topics prevalent in the CRC. Using the SKOS data model (Miles and Bechhofer, 2009) and principles from Linked Open Data (LOD; Berners-Lee, 2006), the CT will provide a language-independent framework for the annotation of domains used in metaphorical mappings. Linking concrete metaphorical expressions with a central semantic resource enables retrieving conceptually related metaphors from different corpora, and comparatively studying semantic domains used in metaphors.