At the Vatican Museums in Rome: "Laocoön and His Sons." It was created around 90 BC ... give or take 70 years ... by an unknown sculptor. When I first saw this I thought it was quite contrived, although well sculpted. But like most sculpture, it gets a lot better when you know the backstory. It's based on a lost play by Sophocles: Laocoön tried to save his fellow citizens by revealing the Trojan Horse, but before he could do so (or after a failed attempt, depends on the version you read) a god who wanted Troy to fall killed Laocoön and his sons: we see him at the point of realization that the snake is supernatural, and that he, his city, and his sons truly are going to die.
The statue was rediscovered in 1506, and was hugely influential on Michelangelo and his peers. More information.