Westerville here. There's a loop you can do around Old Man's Cave that's very cool. It starts with 374 off 33 by the antigue shops. Then just as you pass the main cave entrance and camping entrance take the right to Ash Cave/Cedar Falls. Follow that till it dead ends. Take a right. That road ( name ?) will also dead end. When it does at the little town, take another right and you'll end up back on 374 close to OMC.
The Amish countryside is very scenic too around Holmes County. I take 62 to get there, but notice all the green (scenic) highlighted roads on the state map in that area. Very Hilly and swampy too. Just watch for the buggies. As you know they're flat black and they never put any freakin' lighhts on them at night.