Knoxville was originally built on a bit of a bluff. As the city expanded and Gay Street moved to the edge of the bluff, it used to have a steep drop down to the railyard off Jackson. The city built bridges over top the railroad, which led to a "rollercoaster" up and down for pedestrians and (then-new) vehicular traffic to cross the RR tracks.
Sometime after WWI, the city built the Jackson Ave. viaduct, (I think it was the largest public road project in Knoxville at the time), to cross the tracks without the rollercoaster effect. They built pillars to support the new structure, and built a new road up above the original road grade.
If you go down to the parking lot beside the old RR station in the Old City, you see the sloping road rising up towards the now-elevated Gay St. In the late 80's/early 90's, there was a club scene down under the viaduct. I don't know or remember if it was legal or clandestine, (don't ask why I don't remember
). The old first story storefronts are still under there, along with any basements that existed at the time. From time to time there has been talk of developing into cafes/clubs/stores, but I don't know if anything will ever come of it.
It is a neat block of Knoxville history. I don't know how to access it now, or even if it is safe, but, back in the day.....it was pretty cool. Narrow, sloping, new, unknown, mysterious. Kinda like the rest of my college experience.