Gazing grandly over Trafalgar Sq through its Corinthian columns, the National Gallery is the nation's most important repository of art. Four million visitors come annually to admire its 2300-plus Western European paintings, spanning the years 1250 to 1900. Highlights include Turner's The Fighting Temeraire (voted Britain's greatest painting), Botticelli's Venus and Mars and van Gogh's Sunflowers. The medieval religious paintings in the Sainsbury Wing are fascinating, but for a short, sharp blast of brilliance, you can't beat the truckloads of Monets, Cézannes and Renoirs.