3D modelling technologies, such as photogrammetry and laser scanning, enable detailed and accurate digital replicas of artefacts and structures, allowing for in-depth analysis and virtual restoration without physically altering the original items. Photogrammetry has advanced significantly with high-resolution cameras and sophisticated software, allowing for the creation of highly detailed and accurate 3D models from photographs [13], even if the data collection is influenced by atmospheric and ambient lighting conditions. Concurrently, in the last years, laser scanning technology has seen substantial improvements in speed and precision. Usually, these systems use an infrared (IR) laser source, assuring a higher spatial resolution and precision and a much lower influence by lighting conditions, and the Time-of-flight (TOF) method or the Amplitude Modulated Continuous Wave (AMCW) method [14]. Moreover, recently multi-wavelength laser scanner systems, using more than one laser beam with varying wavelengths, have been implemented to measure not only distances but also reflectance intensities at specified wavelengths for different applicative goals [15; 16; 17]. These systems are particularly useful in applications such as those of cultural heritage documentation and study, where information on colour properties and underlayer materials and treatments are of very large interest. In such a complex frame, in the present work, we present the results obtained by the fusion of data coming from two different prototypal laser systems, an imaging LIF instrument called FORLAB, and a three-wavelength laser scanner based on phase method called RGB-ITR, in the context of the ESA co-founded VADUS project [18]. The VADUS (Virtual Access and Digitization for Unreachable Sites) Project aimed at providing tourists and researchers with the opportunity to explore cultural and archaeological sites that are not (easily) accessible. The main goal was to propose a modern use and knowledge tool that could be able to go beyond human visual perception, offering virtual and augmented reality experiences through accurate and highly defined 3D models enriched with multimedia information. These models reveal hidden aspects of artefacts through the integration of advanced techniques, such as LIF combined with 3D models [18]. One of the sites selected to demonstrate the VADUS concept has been the Casa di Diana (House of Diana) in the Archaeological Park of Otstia Antica (PAOA), close to Rome (Italy). The complex of House of Diana, located in the central sector of the Ancient Otsia excavations, has been chosen because, even if it has easy access for professionals, it is not accessible to the public. Moreover, it provided an ideal case study for testing the effectiveness of these technologies on archaeological contexts characterised by particular complexity. The building, named after a terracotta relief depicting [PERSON] was built in the first half of the 2 nd century AD and over time underwent significant alterations to both the internal walls and the floors, until its final abandonment in the 2 nd half of the 4 th century AD [19; 20]. Discovered and brought to light between 1915 and 1916, it underwent numerous conservation works over time, both to consolidate the walls and to restore the frescoes and mosaics that decorated it. Since many of these interventions are not or poorly documented, the first goal of the diagnostic investigations has been to reconstruct the building's conservation history by identifying and distinguishing the materials and techniques used in the various phases of restoration, also documenting the evolution of restoration philosophies. The second, important, objective was to identify elements of the decoration that were no longer visible due to the progression of the state of decay over time, particularly on frescoes.