PORTAL. - In antiquity, alongside the monumental type, already present in Egyptian and Assyrian civilization, which in the imperial age would develop into the great door-arch of entry to Italic and provincial cities, there persists the type of door with a clearly rectangular cut, framed by a band and surmounted by a tall frieze. The first Christian basilicas drew inspiration from this type, when the absence of the narthex or the quadriporticus does not disturb the door in its essential function. In the portal of St. Salvatore in Spoleto (4th century) even the decorative elements that recur in the framing belong to the Roman tradition.
Given the poverty of the facades, in the Byzantine age the door is simplified to the utmost, often reduced to a projection of the wall surface. The classical tradition, on the other hand, makes itself felt longer in Rome, also because of the abundance of ruined classical buildings existing there, from which it was possible to recover fragments of friezes and architraves for decorative purposes. The disappearance of this use after the 7th century coincides with an impoverishment of architectural forms, so that the door remains of an extremely simple type, architraved or arched, with the frequent use of the discharging arch. The entrance of the chapel of St. Zeno, in the church of St. Praxedes, flanked by two ancient columns, on which a classical architrave rests, testifies in the first half of the 9th century to a return toward the serenity of ancient structural rhythms.
In the Romanesque age the desire for complexity and variety of structural elements is reflected also in the form of the portals. On the framing of the door the arch unfolds, determining a lunette, often decorated. Within the outer arch concentric arches are inscribed, at first projecting. A Lombard creation is the splayed door, in which a series of arches and moldings penetrate into the wall, in the shape of a funnel, with a great abundance of sculptural decoration (door of St. Michael in Pavia, 1st half of the 12th century). The Cosmati give to the doors of their buildings the typical characteristics of geometric rigor and mosaic vividness.
In the Gothic period, particularly in France, the door takes on a very great value in the facade, with the accentuation of the splay and the addition of a strongly projecting gable, which frames the series of arches that have become pointed. In Italy there are characteristic examples in St. Anthony of Ranverso, in the cathedrals of Chivasso and Pinerolo. The abbey of Fossanova inscribes a tympanum in the pointed portal.
In the Renaissance the classical characteristics of the door reappear. Alongside the type of door surmounted by a tympanum, which as the 16th century approaches becomes curvilinear, and the round-arched door, the type of the rustic door is in use, outlined by bosses, without projection, in the wall. The decoration is of the most varied types. Often the door is surmounted by a window, later by a balcony. The broken tympanum, the double tympanum, the increasingly projecting members, in relation to the search for solids and voids and to the dynamic tendencies of 16th-century architecture, bring, beginning with Michelangelo, notable modifications to the form of doors.
In the 17th century the door becomes an element of enormous importance in the facade, whose dynamic structure it follows, adapting itself to its curvilinear course (St. Carlino alle Quattro Fontane) and with the use of the column placed against the wall, and then of the free-standing column, in place of the pilasters (church of the Gesù, St. Marcello). In the 18th century the elements, more or less unchanged, of the Baroque door adapt themselves to the more slender architectural vision. The neoclassical architects hark back to classical or Renaissance examples. - See plate CXXI.
