ABSTRACT:Reconstruction is an action that re-builds a ruin or a non-existing structure trying to reproduce its form and shape at a given moment of its past. Reconstruction of Cultural Heritage monuments used to be common practice during the 19 th and 20 th centuries. However, contemporary ways of thinking and approaching the issue of reviving the past have introduced a lot of scepticism as far as reconstructions are concerned. An attractive alternative is virtual reconstruction, which does not involve any intervention to the existing relics, while it offers all advantages to the curator. In this paper the virtual reconstruction of a non-existing building of the Athenian Agora is described, presented and visualized. All data collected were evaluated and used appropriately for the final product. It is evident that, on one hand, the data collected do not all belong to the target period and, on the other, not all the data necessary to built up the model are available today. Therefore, one needs to carefully select the data corresponding to the period of study and complete them with suitable hypotheses. It is imperative that both tasks must be done in collaboration of the archaeologists and architects responsible for the monument. In this context a hierarchy of the data was developed, based on their reliability as far as their "correctness" is concerned. The data were categorized for their reliability after careful evaluation. The accuracy of the data depends on the source; hence the data which originate from a drawing or from one study of the 3D reconstructed monument are considered more accurate than data which come from a source referring to architectural elements of other monuments or written reports of travelers. Sometimes the data appear in more than one source, in this case they must be checked for their reliability. In cases of remaining artifacts that could be found in the museum and belonged to the building a different approach was followed. They were used to produce 3D models and these were later attached to the final 3D model. From the final virtual reconstruction a short video has also been produced for the better visualization of the result.