Anna Christie happens in three distinct locations: a bar, a coal barge, and the cabin aboard the barge.   The bar has a three sections for different aspects of the scene, including the quiet back room for their big conversations and the second floor with the piano for the smaller scenes.  The coal then emerges from the traps leading to the pit, while the rest of the barge comes in from either side of the stage and the bar disappears behind them.  Then, for the final act, the coal drops back into the pit while the structure rotates and we end up inside the cabin.