This paper presents a case study centered on the virtual restitution and virtual life simulation of a highly complex and endangered heritage edifice: the church of Hagia Sophia, in Istanbul, Turkey (added in 1996 in the annual list of endangered monuments by the World Monuments Watch). The goal of this article is to describe the techniques used in order to achieve a photo-realistic simulation of the selected space and its characters, as well as to point out the challenges and solutions that such a work implies at different stages in production. Most of these issues are mainly focused on the reconstruction of the architecture of the site, but in order to achieve an accurate simulation the social aspect must not be forgotten. The importance o...