We will be spending 31/2 days in the Munich area in mid-October. We will be renting a car and do not need to stay in Munich. Any suggestions? We are a group of 6 retirees who like to be active. We do want to visit Garmisch-Partenkirchen.

If you are renting a car only to visit Garmisch I do not recommend it.

There is a lot to do and see in Munich but if you are wanting to get out in the countryside the upper-Bavaria loop (called that because of the elevation not the compass direction) that takes you out the Garmish Autobahn has a lot to offer. You can go to Garmish (be sure to check the weather at the top before you take the ride to the top of the Zugspitze, it can be socked in). Mittenwald (the violin maker's village) is about 10 miles from GP. You can backtrack a little way then take a cutoff from the autobahn toward the Ettal Monastery, SchlosLinderhof, Oberammergau, the Wiesekirche and then Fussen for Neuschwanstein and HohenSchwangau castles. You can make a loop out of it or come back to Munich the same way you came.

I would take the advice above but when returning towards Munich cut off and go to Berchtesgaden. That is what we did in 2013 after spending 2 days in GP. 2 nights in Berchtesgaden and seeing Lake Konigsee by boat as well as taking the bus up to the Eagles Nest left us breathless with fantastic scenery in the Alps.

Ok - I see you said 3 1/2 days total. Well then, perhaps if you heading towards Salzburg, you can include my suggestion.