This paper presents the results of the geometric and constructive study of the rib vault in the apse of Nuestra Señora de las Nieves Church located in the town of Manzanares El Real (Madrid, Spain). The Dirección General de Patrimonio Histórico de la Comunidad de Madrid (the department of heritage of the regional government of Madrid) and the Archbishopric are carrying out restoration works on the building that have allowed us to develop several researches, like this study. First of all there have been taken accurate measures with a total station. This measurement has allowed us to study the geometric rules and its constructive process. This research, supported on the other studies realised, made possible to identify the project authorship.