The play takes place in Argos, a city in the Peloponnese, a large peninsula in the south of mainland Greece. (Here's a map.) The action begins on the night that Troy is captured by the Greeks. We know this because, in the opening scene, the Watchman on the roof of Agamemnon's palace sees a signal fire in the distance that tells him Troy has been captured. This setting is important for a couple of reasons. Time-wise, by almost coinciding with the fall of Troy, the play takes place at the moment of Agamemnon's greatest triumph; from the perspective of tragedy, this is the perfect moment for him to take a tumble. Space-wise, the opening of the play reminds us that we are not with Agamemnon during his triumph. Instead, we are back on the home front, where things have taken a very different turn during his ten-year absence, mainly because Clytemnestra is in control. On his return, Agamemnon will have to confront these changes, as well as the horrible secrets of the past that linger in his house.