First,,,,, come between late late spring to early fall ;-)
Iowa is not as flat as many people think,,,,, but it sure aint the Rockies ;-)
If your'e a Biker (bycicle), come for Ragbria and pedal accross the state eating home pie and other wonderful things. There are really alot of bike trails around Des Moines.
Iowa State Fair is second largest State Fair (to Texas).
2011 Iowa State Fair | Nothing Compares
Grotto of the redemtion is quite interesting.
Grotto of the Redemption, West Bend, Iowa
The loess Hills are very interesting. Only in China are they larger.
Loess Hills Scenic Byway
If you make the trip,,, Welcome in advance.