COLONNA. - It is a load-bearing element of circular section, generally of marble or stone, with a base and capital connected to similar ones by an entablature or by arcades; it is intended to resist the vertical action of the elements above it (see also ORDINI ARCHITETTONICI). It can also be used in isolation or leaning against walls and piers with eminently decorative functions. The architects of the most ancient Christian basilicas made very wide use of it to divide the great space of the church into several naves.
Notable in this period are the vitineous columns of the ancient basilica of St. Peter intended for the enclosure of the iconostasis, or those banded with foliage in the choir of St. Praxedes. The columns of oriental provenance of the ciborium of St. Mark, with figurations that unfold in superimposed rings, derive from the type of the Roman figured column. Also to be noted at the beginning of the 6th century are the columns covered with ornaments of the ciborium of the priest Mercurius in the church of St. Clement. During the early Middle Ages, spolia columns were used almost everywhere, and it was only in the Romanesque age that columns acquired new and unusual relationships of proportion. Later, at the beginnings of the Gothic, the column often takes on the appearance of a twisted form with three or more elements, and often the twisted forms have different courses within the same column, divided by horizontal pauses into different stretches. Then, especially in Rome as in southern Italy, the shafts are often veined with mosaic. The twisted column disappears in the Renaissance, when the rigidity of the classical orders is re-established. In the transition to the Baroque, the column undergoes some freer interpretation of proportions; Bernini in the baldachin of St. Peter draws inspiration from the vitineous ones but confers new coherence on the motif; Borromini also uses caryatid columns; Fuga covers with metal foliage those of the tabernacle of St. Mary Major. Especially the Berninian innovation had wide resonance also in painted perspectives (Frascati, Gesù). Once the rigid ancient norm of proportions was re-established with Neoclassicism, nineteenth-century architecture made wide use of the column, until the introduction of new building materials, iron and especially reinforced concrete, altogether distorted the character of the original relationships between this and the other architectural elements.
Guglielmo Matthiae