After your hot spring session, why not drop by hell valley? Take a look at the source of your hot spring water. The hell valley is actually a sunken deep valley formed prior to an erruption of a volcano. Please do not attempt to get in contact with the water as the temperature of the water is above 90 degree celcius.
Hell Valley is one of the two sources for Peitou hot springs. Surface temperature of this hot spring is over 90 degrees celcius, and is too hot to be used directly. However the hot spring water is supplied to numerous hot spring hotels nearby. This hot spring is sulphurous type, thus it is smelly. However, it is supposed to be good for healing skin problems.