So what's the 411 on the graffiti wall south of the Arch? Sounds like an interesting photo op. Is it walk-able from the Arch area?
It's a very long floodwall that gets painted and re-painted by the best graffiti artists in the city. Some of the work is absolutely amazing. The location is definitely daytime only and kind of desolate, which translates to scary for me. I'm not aware of any trouble people have had there, maybe someone else can chime in. We have not felt uncomfortable driving up and down the wall with the occasional stop, though.
I did a search on Flickr:
As TTT noted, a sketchy area mostly because it's desolate, bordered by the river, interstates, and abandoned warehouses. Definitely walk able from the Arch. We parked by there a few years back when the Cardinals won the World Series and they had the welcoming celebration at Busch.
There is art in the flood walls both North and South of the arch. The North bike trail runs along the wall and gets more traffic but either way is probably OK during the day. Chouteau ave gets pretty sketchy and it is not uncommon for people to be robbed in that area, not so much right at the river which has a lot of industrial activity, but further West where it starts bumping some project housing. In general unless you are familiar with the area stay North of I-64, and South of Convention Plaza when walking round.