In ancient days in a ravine between hills in Arima Onsen, poisonous water
gushed out of the ground due to the influence of a hot spring. As a result,
whenever the birds or insects would drink water from the pond, they would
die painfully. No one knows exactly when, but people began calling this
place such names as Hell Valley, Bird Hell, and Insect Hell. Now there
is only a stone monument.