Consider popping over to Windsor so you can set foot in Canada. You can take the Detroit-Windsor tunnel or the Ambassador Bridge. Completed in 1930, the tunnel is still the world's only international automobile tunnel and the bridge was the world's longest suspension bridge when it was built in 1929. Even now it is the busiest international border crossing in North America. Even if you don't have a vehicle, you can still go -- Transit Windsor operates a bus service to/from Detroit.
Make sure all your travel documents are with you and in order, sometimes returning to the U.S. can be difficult if they're not.
Windsor has its own casino which is quite popular though I've never been there except to for currency exchange purposes. Another reason to go to Windsor is to have dinner. There are many nice restaurants there including very good Chinese dim sum. If you're 19 or older, you can also go to Windsor to drink. This is an especially popular activity for the under 21 crowd.
Windsor has a great waterfront park area along the Detroit River. Take time to stop and enjoy the great view of the Detroit skyline and water traffic. In the summer you can take sightseeing cruises on the river.
Tip: If you're a non-resident, you can get a refund of GST (7%) taxes paid. Just stop at the Duty Free Shop at the border for your refund OR get your receipts validated and mail them in later. In order to be eligible for a refund, all the following must apply:
-- Total receipts must total at least $200 CAD.
-- Each individual receipt must total at least $50 CAD.
-- Receipts are for qualifying goods e.g. most anything that you can buy and take home with you plus accommodation.
Things such as liquor, tobacco, gasoline, car rental, meals and theater tickets do not qualify.
If you stay overnight and buy a few things, chances are you'll qualify. If you're with a few people, make sure you put everything you buy at a store on one receipt if it will be over $50 when combined.
Drive across the Ambassador Bridge (or take the underwater tunnel) to Windsor. They have a really nice waterfront, with walking paths and cool sculptures, where you can get some nice views of downtown Detroit.
Windsor, Ontario, Canada. That's right, CANADA. A little bit of international flair only a mile over the Ambassador Bridge. Great Restaurants, Great Clubs, Ethnic neighborhoods, Casino Gambling, and the exchange rate is great right now.