Try the Niles Haunted House Scream Park in Niles, Michigan. They have what is known as one of the best haunted themeparks in the midwest. It was named one of the Top 5 Haunted Houses in the country on Yahoo.
The park has 5 attractions plus the midway. There is something for everyone, those who scare easily (*raises hand* I can only handle the Dark Terror-Tory Hayride) to those who love extreme fear. And don't forget about the Gore Store.
So if you are in the area (and it is worth a couple hours' drive) be sure to check it out.
