I'm not sure how far your willing to drive but there's a beautiful chapel in shelby, Ia. It's called wedding glass chapel. Check out their Facebook or website.
You could look at Lewis and Clark monument in Council Bluffs. It isn't a field, but it is a secluded place with a great view.
Or, have you tried Fontenelle Nature Center in Bellevue? They have a back patio that is large enough for a wedding - no water overlook, but beautiful trees.
There is a perfect place our friend owns and he has done weddings out there.
It is called Riverwest Park the web address is:http://riverwestpark.net
It is out by Elkhorn right on the river, flat and open.
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