Hiking is a perfect mixture of a fun activity and minimal time commitment. Karl offers 4 hikes, of which you choose 3 to attend. The hikes start on Sunday morning at 8 AM and, though the syllabus says that they end at 5 PM, the class was often over by 2 or 3 PM. Take the class in the fall: the scenery and weather are great in October and November. In terms of physical effort, the hikes range from moderate to strenuous (Bear Mountain); the hardest part of the class is the "short" 5-mile run you do before signing up for the class. Other than that, I had no complaints. Karl is a good guy: he even prepares Argentinian tea for the class on the last hike. Sure, it was an acquired taste, but the thought was certainly appreciated.