The Arch, was cool!
They have a nice Museum underneath. You ride up in a little egg like thing, it seats 5. It takes four minutes to get to the top. The egg clicks and sways a bit as it adjusts on the way up, like a ferris wheel. You have a little window to look out on the way up, but you only see the superstructure. Then at the top they have an observation deck. You can look out both sides. It sways a bit up there like the Eiffel Tower did. It was worth fitting it in.