Stretching nearly three kilometers across West Lake in Hangzhou, China, the Su Causeway is one of the lake’s most iconic features. But it began as a massive engineering project. During the Northern Song Dynasty nearly 1,000 years ago, the poet-official Su Shi (1037–1101) oversaw the dredging of the lake, using the excavated mud to build the causeway. More than just a pathway, this project reshaped the lake itself. Today, the causeway—built from mud—still carries everyday life across the water.