Watch the shadows. We know that the sunlight in lower Manhattan was coming from the east. The shadows, therefore, were pointing to the west. In the opening scenes the shadow of the camera is on the actors, meaning that we're viewing the scene from the east with the sun behind us. Then look at the background, the trees have shadows pointing to the left, meaning that left is to the west. So we're viewing that scene from the south looking north. From where in lower Manhattan can you look to the north and see a large grassy meadow with water and a shoreline beyond with a building skyline?