The Fortress is an 18-hole public golf course in Frankenmuth, Michigan, built in 1992 and designed by Dick Nugent. It sits in the $$$ (premium) price range for golf in Michigan. The season runs Apr 1 to Oct 31. Tee times can be booked 1 year in advance. Guests are welcome.
Details like fees and seasons change, so call the course before you head out.