Critic and art historian Andrew Graham-Dixon travels from southern to northern Spain to tell the story of some of Europe's most exciting and vital art. He journeys to the country’s scorched centre to explore Spanish art of the 16th and 17th centuries. From the mystical world of El Greco to the tender genius of Velazquez, this was a moment so extraordinary it became known as the Golden Age. But beneath the glittering surface was a dark and savage heart.