This work focuses on a harvesting of various metadata elements that exists in informally and heterogeneous schemas for the documentation of immovable monuments used from many Greek public services, working in the field of the built heritage. A series of crosswalks between the metadata collected and schemas of official standards that used widely to describe architectural works, allowed us to identify which official metadata schema, would fit better in these records, in order to reduce syntactic and semantic heterogeneity and in parallel to reveal gaps and shortcomings of these standards in the description of immovable monuments.