Loggias of thirteen bays were built as a long gallery for the papal apartments in the Vatican to Bramante's design. They were started in 1509 and, after Bramante's death in 1514, were completed under the supervision of Raphael. The decorations combining biblical and classical forms were completed between 1517 and 1519 by Giovanni da Udine (who specialised in decorative forms, painted and in low-relief stucco), the painter, Giulio Romano, and others from the workshop under the supervision of Raphael.
'Arabesque' refers to the style of flowing floral decoration known originally through Arab, and therefore Islamic, examples which lack any representation of human or animal forms. Grotesque was the word used for the similar decorations of the recently discovered underground rooms ( grottesche) surviving from antiquity. Vasari in his life of Giovanni da Udinerefers to Raphael and Giovanni da Udine visiting together the recently discovered 'Domus Aurea' of Nero, and this was a source for Raphael's decorations for the Loggie ( Vasari, Le Vite, Testo V.448).
Raphael 's 'arabesques', like those of Classical antiquity, and like the mosaics of the fourth-century Christian church of Santa Costanza in Rome, included human and animal forms, and so might be better described as grotesque than arabesque. The grotesque style of decoration became popular in England and France through the work of Chambers, A Treatise on the Decorative Parts of Civil Architecture of 1759, and Adam, Works in Architecture of Robert and James Adam, Esquires starting in 1773. Summerson, Architecture in Britain 1530-1830, p. 263, argues that their knowledge of Raphael was an important influence on the development of what came to be known as the Adam style.
Elsewhere Ruskin stresses the pernicious consequences of Raphael's arabesque / grotesque.