Spoiler
A conversation pit is an architectural feature that incorporates built-in seating into a depressed section of flooring within a larger room.
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The conversation pit was popular from the 1950s to the 1970s, seen across Europe as well as North America. Modernist architects Eero Saarinen and Alexander Girard used a conversation pit as the centerpiece of the influential Miller House (1958) in Columbus, Indiana, one of the earliest widely publicized applications of the concept. A red conversation pit (since covered, but recently restored) was later incorporated by Saarinen into the 1962 TWA Flight Center at John F. Kennedy International Airport in New York.
These fell out of favor cause drunk people fall in so they became insurance liabilities
I have to imagine it also lost favor as living rooms began to be centered around the TV