We had a blast checking out Wynwood Walls in Miami. It is a neighborhood of one story warehouse buildings that were pretty much abandoned. A wealthy developer bought a couple of the buildings and got graffiti artists to go crazy on the buildings and made it part of the Miami Basel Art show. The rest you can guess. Stores and cool restaurants are popping up there. The neighborhood is not declining anymore. Here is the official site. You can see my photos of our visit below.
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Map to Wynwood Walls (Note: travel times varies widely based on whether it is rush hour or not. Check the map for estimated time when you want to go.)