Bankokei (万古渓)
This is a short hike (under 1 mile) to a waterfall. There are 2 small swimming holes along this hike. It's a good stop to cool off if you are in the area already. If you bike, this is off route 42 and makes a good place to take a break and hop in the water (23 miles from base). Driving directions are here, although there is no parking area. The trail starts at the corner of the road by the signs in the first photo below.