415 W. Washington, with a fading sign from when it used to be the County Road Commission yard. Now it houses the City's division of Park Operations, street-sign and radio shops, etc. Insiders just call it "415."
I sometimes hear ideas about converting this into artist space. I love the idea in principle; but when I worked at NAP, any time we would talk to folks at Park Ops, they would say, "this building needs to be condemned." I didn't look that closely, but without some renovations I'm sure the heating bills would be immense.