A short walk up Zhongshan Road from Beitou MRT, the Thermal Valley — locally Diyu Gu, "Hell Valley" — is the source of Beitou's hot springs. Sulphurous green water steams visibly from a small rocky pool, reaching a constant 90°C and giving off the characteristic rotten-egg smell that hangs over the whole district.
A wooden boardwalk loops around the pool; bathing or touching the water is not permitted, but the rest of the valley is a pleasant fenced park of lawns, koi ponds and shade trees. Free entry. Visitor numbers are highest in winter when the contrast of warm steam and cool air is most dramatic.