Assignment: Rhythm
I think the rhytm comes from the pattern of the glass pyramid, the way it is lit at night, as well as the straight reflection of the smoothened water due to the long shutter speed, with its odd curves right at the edge because it was a rounded edge. The couple in the back must have stood still for those 30 seconds, which was pure luck! It sure adds some intimacy and romance to the shot in my opinion.
EXIF:
Camera: Nikon D80
Lens: Nikkor 18.0-55.0 mm f/3.5-5.6 DX VR
Exposure: 30 sec
Aperture: f/22.0
Focal Length: 18 mm
Exposure: +0.55
ISO Speed: 100
Exposure Bias: 0 EV
Flash: No Flash