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.
for the biggest budget possible for wheelchair accessibility i'm thinking like a wheelchair-sized square is missing from one of the couches, and in that square is a wheelchair-sized elevator platform you can roll your chair onto, then lower the mini-elevator into the pit to be at the same height as the rest of the couches, and then when you need to leave activate the lift back up again and roll backwards out of the pit-levator
with like mini-rails on the front three sides of the lift so you can't accidentally roll into the pit