Here's Appleton, home of Joe McCarthy, Harry Houdini (sort of), Willem Dafoe, and Greta Van Susteren (ew

)
Best pic of downtown skyline I could find
This is the closest I get to a castle..."the history museum at the castle", which always features a Harry Houdini exhibit. I think it used to be a masonic temple.
This is the 'Heathstone House' museum, it was the first residence in the world powered by a hydroelectric station (or something like that), located on the Fox River. I drive by it a lot when I take the downtown route to work.
Here's an aerial view of part of the Fox River. It's an old pic though, they redid the bridge, and there is a roundabout at the intersection in the lower right now. I actually live only about a mile or so away from Telulah park (which has a great disc golf course). I traverse this bridge often when going downtown, or taking the non-highway route to the west side of town.
A little bit south of here is Oshkosh (yes, home of Oshkosh, b'gosh). Also home to the EAA airventure museum, which during one week in the summer hosts the EAA Airventure airshow, which also makes it the busiest airport in the world during that time (Wittman Airport).
Travolta at EAA
My hometown of New London, WI doesn't have much, but due to the large Irish population they do change the name of the town for a week around St. Patricks day. The 'American Water Spanial' was developed in the area. With 2 rivers it's a fisherman's town. Has lots of swampy areas too.