Huili Ancient Town, at the southern end of Sichuan, was founded in 111 BCE and named for its role where "rivers and plains converge." A key stop on the Southern Silk Road, it was long known as the "Key to Sichuan and Yunnan." It is the only well-preserved Ming Dynasty military guard town in China. Streets radiate from the Bell and Drum Tower toward four gates, forming a checkerboard of four streets, three passes, and twenty-three lanes. The north gate tower, Gongji Tower, has walls that predate the Yuan Dynasty as earthen walls, refaced with stone in the Ming—a rare "Yuan foundation with Ming superstructure." Kejia Lane, 156 meters long, produced over 390 high-level scholars in the Ming and Qing. Ming and Qing residences, guild halls, and ancestral temples remain, with grey-tile roofs and stone-paved streets.