Hei Pi River cobblestone illustration

Quick answer：

The 'Hei Pi River cobblestone illustration' likely refers to an artistic representation or photograph of cobblestones found along the Hei Pi River. Cobblestones are small, rounded rocks that are naturally occurring and are often used in construction or as decorative elements. The Hei Pi River could be a specific river known for its cobblestone features, and the illustration could be part of a geological study, an artistic project, or simply a documentation of the river's natural beauty.