This thread is incorrectly named. It should be WORST unwalkable course. My nomination would be Morgan Hill In PA, just south of Easton. A few good holes and several ski slopes as well !
Best Challenging Walk - Yale, CT. Some pretty big hills on a number of holes and tough uphill from the 9th green to 10th tee and then again to the 10th Green, and then again to the 12th green. You get the picture with 18 possibly the biggest hill of all.
Played and walked about six Outpost Club - Punchbowl events in October, 27 holes with two shotguns out and back to the middle of the course and back to the clubhouse from the aforementioned 9th. About 12.5 miles of walking. Not sure I could do it now, and play any good !
The heat takes it's toll on me, this summer I'm lucky to walk the front at Springdale and ride the back, even though it kills me to have to do that.