Huangquan, the Yellow Springs, is the oldest recorded Chinese term for the realm of the dead, attested in Chinese literature well before the Buddhist-influenced bureaucratic underworld of Diyu took shape, and named for the yellow-tinted groundwater and clay found in parts of northern China, imagined as an actual physical location reached by travelling downward beneath the earth.
Early classical references, including the well known Zuo Zhuan account of Duke Zhuang of Zheng, who swears never to see his mother again "until we reach the Yellow Springs" after a bitter falling out, then arranges an artificial tunnel to a spring so the vow can be honoured technically while the two are reconciled, show that the term functioned in early Chinese literary and historical writing as a vivid, concrete idiom for death and permanent separation, similar to how English speakers might once have said "until the grave" or "in the hereafter". Unlike the elaborately administered Diyu that later absorbed it as one of its features, classical Huangquan carries relatively little moral or judicial machinery of its own; it is primarily a place, not a court, marking simply where the dead reside once they leave the world of the living.