<p>This paper presents the survey of the Baptistery of the Collegiata Museum (Castiglione Olona - Italy), painted by Masolino da Panicale in 1435. Surveying activity was carries out throughout the use of combined digital techniques of documentation (topographic measurements, laser scanning, digital photogrammetry, thermal imaging, digital photography). Different data were collected inside and outside the Baptistery following a multi-resolution reconstruction that ranges from the whole Baptistery up to small details. Laser scans were also used to obtain a digital representation of inner volumes of the structure. Registered scans were uploaded into a modelling software, in order to produce a 3D model based on scan data, increasing the correspondence with the existent building; this model can be used to better understand the volume arrangement, also for educational and dissemination purposes. A particular attention was devoted to documentation of graffiti scratched onto the frescos, since their presence is a significative evidence of the history of the building. A digital-based workflow was set out in order to assure high quality outputs in respect of the conservation needs.</p><p>This multi-resolution approach proved to be a suitable solution when dealing with features, such as ancient architectures, with a high number of complex details to be correctly recorded and joint together as starting point and support of historical researches. Results and scope are here presented.</p>