The work presented here was developed as a major training activity of the Seminar of Urban Survey by the students of the XXVIII and XXIV cycle doctorate in Science and the Representation of Survey. Survey is the main tool to understand an architectural work and the several features that rule its spatial concept. The architectural complex of Saint Yves at La Sapienza, original place where was based the University of Rome, is full of interesting information to be learned. The building was designed by Francesco Borromini and implemented in the second half of XVII Century: its shape is characterized by a strong centralization, which is the result of the plan design. The plan of the building was born from the composition and interaction of different geometrical shapes, like the circle, the triangle and the hexagon. These shapes are all pivoting around a strong center but creating a complex weave of lines and curves around it. Centrality is enhanced by the giant coupled responds forming six huge pillars joined by the projecting cornice, directly leaned on the Corinthian capitals of the aforementioned columns. The last fillet of the cornice highlights in silhouette the strong intention of the designer, expressed by the multi-curved shape at the base of the dome. Finally we reach the sky at the top of the dome, where shapes melt in the light coming out of the big windows: here moldings are the only elements which keep together the big vertical columns rising from the ground and disappearing in the shadow. The base of the dome gets together the complexity of architectural elements below, reducing it, as the eye rises to the top, to the simplicity of the circle at the base of the skylight turret. This spatial concept, which is like inviting to look up to the “starry sky of the dome”, expresses itself also outside the building through the geometrical concept of the skylight turret. The turret is set up on a circle at the base and rises up following an helicoidal trend, being decorated continuously from the base to the flamed crown at the top. The completion of the turret is represented by a spherical element, probably symbolizing the Globe, suspended above the flames, which are symbolizing the Christian Charity operated by Saint Yves and embodied by the Pope. The entire complex is crowned by the more explicit symbol of the Christian tradition which is placed next to the sky: the Cross. In the architectural complex of Saint Yves, every decoration lives on its own, but its position respect to the whole building enhances its symbolic value, more than the simple decorative one. The virtual reconstruction, both in a bi-dimensional and tri-dimensional way, of the building of Saint Yves at La Sapienza, has been carried out only through a complex integrated survey methodology, made with long-range 3D laser scanners and high-resolution cameras. After some preliminary elaborations of the data resulting from the survey, like organizing and selecting all the points scanned, it has been possible starting the effective virtual reconstruction. Through the analysis of survey data and the selection of appropriate projection planes, horizontal and vertical sections of the model have been extracted to better understand the geometrical concept. This allowed a critical interpretation of the architectural complex, understanding even the most complex shapes and reducing them to simpler ones. From a practical point of view, the tri-dimensional reconstruction has been executed through an hybrid process, melting the geometrical precision of NURBS surfaces, concerning the architectural aspects, and the adaptability of polygonal modeling applied to the organic shapes of the decorations. This methodology allowed to deeply understand the articulated geometrical solutions designed by Borromini, representing a base for further analysis and studies on these issues.