Alastair Sooke follows in the footsteps of Rome's mad, bad and dangerous emperors in the second part of his celebration of Roman art. He dons a wetsuit to explore the underwater remains of the Emperor Claudius's pleasure palace and ventures into the cave where Tiberius held wild parties. He finds their taste in art chimes perfectly with their obsession with sex and violence.The other side of the coin was the bombastic art the Romans are best remembered for - monumental arches and columns that boast about their conquests. Trajan's Column in Rome reads like the storyboard of a modern-day propaganda film.Sooke concludes with the remarkable legacy of the Emperor Hadrian. He gave the world the magnificent Pantheon in Rome - the eternal image of his lover Antinous, the most beautiful boy in the history of art - and a villa in Tivoli where he created one of the most ambitious art collections ever created.