Yomogi Valley in the manga.
Yomogi Valley is a volcanically heated valley somewhere in the wilds of Japan, the rocks of which are noted as being very good for use in moxibustion, the medicinal application of heat to cure sickness and soothe pains. According to Genma Saotome, the local wildlife especially uses Yomogi's moxa-rocks to cure many of their ailments; monkey backaches, sprained bear ankles, deer birth pains and fish myopia are all examples he gives. Genma and Ukyo Kuonji bring Ranma Saotome here to see if the moxa-rocks can be used to reduce or even cure the Ultimate Weakness Moxibustion that Happosai has afflicted Ranma with, reducing his strength to that of an infant's. To their disappointment, it fails; the only cure will be to get the moxa-chart back from Happosai so that somebody can burn a countering moxibustion onto Ranma's back.