The Fenelon elevator in Dubuque is pretty neat. I can't say it's as exciting as a roller coaster, but the views of the Mississippi are incredible. https://www.fenelonplaceelevator.com/

The National Mississippi River Museum and Aquarium in Dubuque is interesting too. They have old river boats there in the summer that you can tour, and the inside exhibits on the geology and wildlife of the Upper Mississippi are incredible. Really great interactive exhibits for kids, but I also enjoyed it as an adult. https://www.rivermuseum.com/