Iowa's first LEGO Store recently opened at Jordan Creek Town Center and my son loved visiting today. The store has a few areas for kids to build, including a Duplo area. There's also a Pick & Build wall and a Build a Minifigure area (3 minifigures for $9.99).
We've visited a few LEGO Stores in other states (Florida, Kansas, Minnesota) and I'd say Iowa's is pretty comparable. Although, my boys love the one in Orlando where you can build vehicles and race them.
