Discovered in 1506, the marble group known as the Laocoon was originally in the palace of Titus and is praised by Pliny as being 'of all paintings and sculptures, the most worthy of admiration'. It is now in the Belvedere courtyard of the Vatican Museum, Rome. See Haskell and Penny aste and the Antique, Yale University Press 1981, pp.243 - 247.
Laocoon was a Trojan prince and priest of Apollo who tried to stop the Trojans from opening their gates to the wooden horse. He was killed, along with his two sons, by serpents who came from the sea, sent by either Apollo or Athene.