North West Porch of St Mark's, Venice.

Ruskin’s largest and most famous architectural watercolour, this was the most important product of his stay in Venice over the winter of 1876-77. If the Ducal Palace was to him “the central building of the world,” then the basilica of St Mark came as close as it stands in reality, “the most magical and most mysterious of churches.” It provided the subject for dozens of drawings in connection with The Stones of Venice, including two large studies of the very differently detailed north-west and south-west angles, facing the piazza.

Since regularised by later generations, the extraordinary façade fascinated Ruskin, as epitomising “the most perfect Byzantine Romanesque,” and he was appalled to find work of wholesale ‘restoration’ well advanced in 1876. He was particularly distressed that the last of the thirteenth-century mosaics, in the roof of the fifth bay of the portico, was under threat of destruction, and this precise but also beautiful watercolour is to a large extent a labour of love in recording the decoration of this porch. The Byzantine carving of stylised peacocks, at the top left, also meant much to him, as the motif used to embellish the covers of The Stones of Venice.