American Falls, Niagara Falls
Take a drive OTR. Over The River. To the States. There is shopping, but I think the best views are from the Canadian side. There is more to do there. But the views from the American side are amazing. Make sure you have ID, you are crossing an international border.
If time allows, don't forget the New York side of the falls. It is such a contrast to the Canadian side. Although the view of the Horseshoe Falls isn't the greatest. You can get very close to the American Falls. While the Candian side is all built up with souvenir stores and museums, the American side is mostly a park. In fact, it is the oldest state park in the United States. You can walk right along the rapids leading to the falls. It is very peaceful and natural. Also, the view from the observation bridge is spectacular, if you don't mind heights!!!!