The rest chamber on Stratos is furnished with the iconic "Ribbon Chair" by French modernist designer Pierre Paulin, upholstered here in day-glow orange.
This was one of the first TV roles for football star Fred Williamson, who later became a prolific film actor.
According to John M. Dwyer (on the TOS season 2 DVD special features), the metal artwork and sculptures that appear throughout the city were mostly parts of metal furniture, like tables, etc. that he had rented from "a guy up in Topanga Canyon", minus the glass tops, and much care had to be taken to return them in their original condition.
It is interesting that Jeff Corey was cast as Plasus, the leader of the privileged people on Stratos. For a number of years he had been blacklisted from working for allegedly being a Communist.
The story line is similar to Metropolis (1927) about a two class society where the upper class lives in the utopian city Stratos in the sky, enjoying their privileged life, while the cave-dwelling Troglytes' only existence is working in the mines for the pleasure of a few - which is a key philosophical topic about 'the needs of the many outweigh the needs of the few' in the Star Trek universe.