Camera reconstruction is one of the major problems in computer vision. Software systems in that field uses mathematical camera models, or virtual cameras, for example, to interpret and reconstruct the tridimensional structure of a real scene from a set of digital pictures or videos or to produce synthetic images with realistic looking. Computer vision technics are applied together with virtual reality technics in order to originate new types of applications called augmented reality applications, which use virtual cameras to combine both real and synthetic images within a single digital image. Among the many uses of these types of applications, this work has particular interest in those concerning augmented visits to buildings. In these cases, pictures of buildings — typically old structures os ruins — are reconstructed from virtual models that are inserted into such pictures allowing one to have the vision of how those buildings were on they original appearance. Within this context, this work proposes a semi-automatic and efficient method to perform such reconstructions and to register virtual cameras from real pictures and models of buildings, allowing comparing them through direct superposing and making possible to navigate in a tridimensional fashion between the many registered pictures. Such method requires user interaction, but it is designed to be simple and productive.