Muammar Gadhafi lives in the form of a stenciling on the whitewashed walls of a viaduct at Hubbard and May streets.

He’s dressed in his colonel’s uniform — his hair curling out from beneath his military dress hat — holding a sign with a bit of wordplay that indicates he might still, even now, have a thing for Condolezza Rice. Admittedly, I smiled a bit when I saw it.

We live in a city of viaducts and underpasses — a legacy of our time as railroad capital of the world. Viaducts separate “here” from “there,” “us” from “them.” They mark the boundaries of our neighborhoods. But their white-painted walls — better to reflect light and convey safety — provide a big, blank canvas for art and messages that are sometimes crude, thoughtful, humorous or mysterious. Just like the city itself.

I stumbled on this message painted on the side of a Metra embankment near 86th Street and Vincennes Avenue about two months ago. The now-removed work references artist Jeff Koons’ 1980s piece Ushering in Banality, but beyond that I’m clueless. What do you make of it?

Back to the viaduct at Hubbard and May streets. A few days ago, this tribute could be seen: