The lines of the curb act as leading lines to the main subject, The Pier - Nikon D300 Nikkor 80-200mm @ f/5.6 ISO 200 1/500thUsing leading lines is one of my favorite composition techniques. In the photograph of The Pier above, everything points to the main subject drawing the viewer's eye across the full length of the frame. The entire foreground of the photograph uses the curb as a leading line to the focus of the image. If there was no curb and just black pavement, then having such a large empty foreground would be a waste of space in the frame. However, using the curb as a leading line adds another element of interest to the photograph besides The Pier itself.
Additionally, I used a titled axis composition style to add yet more interest to an oft photographed St. Petersburg landmark.