CUSP. - The term c. (or spire, pinnacle, arrow) commonly designates the highest part of a building that ends in a point. Cusps of this kind are found in medieval monuments, and particularly in bell towers. At first they had little elevation and the form of a cone or of a square pyramid; later of a pyramid with a polygonal base. They were built of stone or of timber covered with lead. Little elongated during the Romanesque period, cusps became very sharp in the Gothic, sometimes reaching a height equal to that of the parts of the building to which they serve as a termination. Still in Gothic architecture, cusps assumed dimensions so large as to have windows ample and ornate enough to give them the appearance of stone embroidery. The decoration of the spires was often completed by cruciform finials, crockets or rampant leaves, placed along the edges. Among the many, one recalls the pierced spires of the cathedrals of Strasbourg and Burgos.
In Italian Gothic one distinguishes principally the spires of the cathedral of Milan, erected in various periods (the tallest, which supports the famous Madonnina, is from the 18th century), which present an interesting example of stylistic mimicry. Among modern constructions one should remember the terminal pinnacle of the Mole Antonelliana in Turin and that of the dome of S. Gaudenzio in Novara, both by A. Antonelli, and the conical cusps of the bell towers of the church of the Sacred Family in Barcelona.
By cusp is meant still more generally an architectural motif whose fundamental line is an acute angle. Thus there are monocuspidal, bicuspidal, tricuspidal, polycuspidal buildings, according to whether they end in one, two, three or more cusps.
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Vincenzo Golzio