EHEM aims to build digital models of historical monuments with a twofold objective: to monitor them and to leave a trace of their present state and future evolution. We intend to achieve this by creating 3D architectural models, based on LIDAR scanning and photogrammetry; which incorporate the reconstruction of the painted wall surfaces and their natural and artificial illumination. Part of the creation of these models relies on engineering research: while we don’t need a visualisation of a video game we do require a digital facsimile. These models are based on scrupulous historical, philological, theoretical, and field investigations: our proposed reconstructions can not be based on historiographical clichés or on superficial analysis of data. Through an interdisciplinary methodology we strive to create an instrument that allows us to protect and monitor monuments. In order to preserve medieval pictorial and architectural heritage, we must move from recreational to conservative uses of technology.