Cyclorama
A water tank sits in front of this cyclorama at Universal Studios in L.A. It is drained in this photograph so the crane can do its work, but normally the cyclorama provides a sky for model ship battles of all ages. I understand that the closing scene of the Truman Show was filmed here – the rupture of the picture plane providing the denouement of the story (in this case the image plane and picture plane effectively being the same thing).
You get an idea of how deep the tank is from the crane in the top picture.