It's a cool building and I was able to tour the three floors open to the public. The chambers of the Iowa State House of Representatives and Senate were both closed, but you could look in through the windows, so that was cool to see. There were several displays and exhibits discussing the history of politics in Iowa. There's also a very cool spot you can stand and hear your voice echo. Move a foot off the spot, seen below, and you can't hear your echo anymore.
There are several monuments and park areas around the capitol building you can tour as well. The best part? It's free, including parking! My kids weren't with me on this trip, but I picked up a souvenir book of all U.S. capitol buildings that can be stamped on each visit. Right now it has just the Iowa capitol building stamp, but I'm looking forward to taking my kids to view a other state capitol buildings. My 10 year old was excited to see the book when I came home and is already looking forward to visiting one of the state capitol buildings and getting the book stamped!