Most of the information that Siret recorded on each of the archaeological sites he studied, the core of his archive, is either part of a larger group of materials devoted to a generic theme or filed as separate documentation on each site.
The first type is included under the heading of Studies and dossiers, while the second, though also found in the "Field journals" which form an independent documentary series, is the category that concerns us here.
Siret produced notes, maps, sketches, diagrams, bibliographic references, texts, drawings, photographs and other material for each archaeological site he studied and stored them in separate folders: some of these are simply compilations of data, but others also include brief write-ups of the contents.
The folders of the most significant sites, such as Villaricos, Almizaraque and Los Millares, have more abundant and detailed documentation.