This paper describes an interactive platform for the semantic annotation of oriented iconographic sources based on an accurate 3D model structured according to spatial and temporal features. This platform, called LOCUS IMAGINIS, provides access to cultural information about monuments by collecting personal snapshots taken by visitors. In particular, the platform enables to perform two actions. Firstly, pictures are added into the database: visitors manually align images to the digital model of the monument and than, by means of automatic procedures, images are enriched with 2D semantic annotations that are projected from the 3D model. Secondly, the collection of semantically-enriched data can be queried: when visitors select 2D images of the database, these are oriented in the 3D scene and superimposed onto the 3D model. In this way, this tool provides access to textual and graphic information describing the photographed site (semantic, spatial, temporal features, etc.). Moreover, visitors can interact both with images and the 3D-model to highlight building parts by color. Accessible on-site and on-line, this tool can create awareness about conservation and is adapted to all kinds of audience: students involved in educational workshops, visitors needing to extend their visit, and documentalists interested in the consultation of the iconographic corpus