A lagoa de São Marcos, Veneza

Paul Signac had spent about 20 years as the leading theorist of pointillism, the method of building a picture from small dots of pure colour that the eye mixes at a distance. By the time he painted this view of the Venetian lagoon in 1905, he was loosening his own rules. The strict dots have grown into broad, mosaic-like tiles of blue and green, laid down more freely. He had visited Venice the year before and come home with watercolour studies, then worked the oil up in his studio, so the picture is less a record of a place than a chord of colour. The domes and towers of the city dissolve into shimmer across the water. Signac cared more here about how warm and cool tiles vibrate side by side than about drawing Saint Mark's basin accurately.