The opening in the floor above is a curve and the spiral stairway to the casino below produces a second curve that results in a curve within a curve. Lights in the casino on a Royal Princes Cruise Ship, taking us to the Caribbean Sea, light up the curve of the spiral stairway to the casino. Nikon D850 camera, Nikkor 10-24 mm f/3.5-4.5, focal length 12mm, 1/30 sec @ f/5.6, ISO 800