Nowadays, when people talk about BIM software, they refer to new constructions, made of regular elements and standard parameters. The question is: what happens when one, instead of a new building, considers an ancient or existing one? To answer this question, the possibility of using effectively the BIM process for the maintenance and the conservation of Cultural Heritage has to be evaluated. In particular, the research examines the case study of the archaeological site of the Sanctuary of Diana in Nemi (Rome), which is an important example in the National Heritage. The final product consists of a parametric model, where one can find, embedded in a database, all the information about the elements for the management of conservation projects. Highlighting positive aspects and existing limits, in order to contribute to further studies on the subject, leading to a mandatory implementation and use of this software, even in relation to future European legislative framework.