Great pics Ned! Would love to see some of those in person. I think we may have one up north of us that's been restored, but can't recall any others. Most are old steel truss bridges that were formerly rail road bridges.
edit: A quick search and didn't find any, but came across this site:
The coolest one is probably the 8th street tunnel, which was buried and forgotten about until a excavation for new building unearthed part of it. They have been considering making it a museum at some point. A few older pics showing each end of the tunnel, the one with the trolleys coming out is now a part area with a fountain.