Fort Michilimackinac
Both in town and and just outside town there are historical features waiting to be explored, from Fort Michilimackinac to Old Mackinac Point Lighthouse on to Old Mill Creek will take you the better part of the day.
Day two would be the day for the trip to Mackinac Island via one of the many transit companies available to you. More history waits for you there all over Mackinac Island. Also once again there is fudge to be had, the fudge shops there realized some years ago that by installing exhaust fans over the front door to the shop they could entice more prospective customers into the shop. Be warned that since the primary mode of transport for goods and people on Mackinac Island is the horse there is usually also a far amount of "spent horse fuel" about so this can indeed make an interesting combination of odors. The island does maintain a fleet of hardy souls that follow behind the horses to try and keep the streets clean. Given the number of horses and the number of scoopers they do an admirable job. You can walk, bicycle or take a carriage tour of the island to get around. Those that are used to horseback riding can visit a livery and rent a carriage if you wish. History abounds as they say, enjoy the day and watch were you step.
On day three it's time to go to the Upper Peninsula to so some sight seeing. The Soo Locks are about one hour past the bridge on I-75. The city is actually called Sault Sainte Marie, and to confuse things just a bit there is one on each side of the border there in the U.S. and Canada. The Soo Locks enable the shipping that transits the Great Lakes access to Lake Superior when travleing in the upbound direction and the materials from the shipping ports of Lake Superior access to the rest of the world without being off loaded at the St. Marys River where the elevation between Lake Superior and Lake Huron change. Stop at the locks and watch the ships go by, to those of you from elsewhere in the world they are ships, you will find that most native born Michigan residents call them "boats" and the ocean going vessels plying the lakes are "salties". Just as a fun fact a "saltie" is required to take on a lake pilot when entering the Great Lakes. Head west from the Soo over to Whitefish Bay and take in the Great Lakes Shipwreck Museum there and amble to Taquamenon Falls to finish the day. A stop in Newberry on the way back to Mackinaw City for dinner and then back to your base in Mackinaw City.
Historic Mill Creek Discorvery Park
While still retaining its demonstrations of the historical saw mill and the miles of great hiking, Historic Mill Creek has added a popular new attraction to their park. The Adventure Tour is a guided tour that shows off the natural wonders of the park in and fun and exciting way. Visitors are taken up across an open bridge, getting a tree's eye view of the creek. Visitors also have the opportunity to climb up a climbing wall and explore the different birds that inhabit the trees of Mill Creek. The tour culminates in it's most popular attraction, an exciting ride down the zipline. Flying like and eagle, visitors soar across the Mill Pond and land safely on the platform across the pond.
Municipal Beach
Lets face it by day 4 you need a vacation. You may have a hotel with a pool or one on the beach, kick back and take it easy. If no beach or pool Mackinaw City does have a Municipal Beach, take Central Avenue west out of town make one left turn and if you don't stop you will end up in the water. Continue along the lake and it will take you to Wilderness State Park one of the most popular in the state. There are beaches there along with hiking trails if you still want to do some discovery. A daily or annual permit is required to enter the park, a few dollars for a day or at this time $24 annually.
This is the ideal jump off point for trips throughout not only the tip of the Lower Penninsula but a large area of the Upper Peninsula is within an hour or two drive time from Mackinaw City. There are shops spread all around town that for the most part offer the standard tourist fare, nothing too extravagant.
fudge shop
We can't let the fudge shop go without being mentioned as this seems to be the Straits area's largest export. Partake of the free samples and when you find the one that you like buy it. To say that one is better than the other is going to lead to countless and eventually futile edits so lets leave it at that.