4I: What's that structure?

As a commuter, I walk past this structure located on Farnam Avenue just ahead of the commuter parking lots and by Brownell hall. This structure, having a circle and a smaller circle inside, then surrounded by stone rocks was an interesting part of my walk to campus every day.
I thought it was interesting because although I pass it every day, I don't really know about it. I figured out that it is Nancy Holt, End of the line/West Rock from the year 1985, and it's made out of stone, masonry and steel. I remember in June when I had orientation, our group took a photo by it and I thought it was really interesting and now I know what it's all about!