DOI: 10.7764/RDLC.16.2.202This study continues the research taken by the teacher Cassinello, Doctoral Thesis "Seismic rationality in Gothic architecture: structural and building types" (Cassinello, 2005), where she checks the special constructive facing earthquakes configuration of Spanish cathedrals, subdividing them in structures Types A or B. Types B have large spandrels on the arches, flat terraces, hidden buttresses and horizontal facades with very vertical windows. The target is to show how these facades of cathedrals and fortifications in the Spanish Mediterranean have special facing earthquake´s configuration being the essential key for the building stability. In order to do it we select and analyse various samples. The Method of the equivalents and horizontals forces and the Analysis of confined masonry defines the design´s principles founds in these facades. Analytical methods relating horizontal areas of façades and areas of buildings, or vertical and horizontal spaces between windows and graphic methods with parabolic arcs or compressed prisms saving the vertical windows provide us comparative results. His analysis allows us how to classify the ability of each façade facing earthquake forces and drawing conclusions that demonstrate this special design.