Here's a photo from 1995 of the 30 year bond pit in the CBOT's old financial room. Although I never saw the old bond room while the CBOT was in there, in 1999 I did get to stand in the 30 year pit at the CBOT for a brief time w/a broker who executed some biz for the desk I worked on at the request of the Managing Director of the firm so I could see how tight the market was and how it flowed. Although it was only about 15 minutes I got to stand and observe, it was amazing and something never to be forgotten. Thinking of how massively large it was and completely packed w/people it's amazing in retrospect that something like it even existed. In the photo the market is 9 bid at 0 if you were wondering.
While on the topic of bonds, here's a 1987 NYT article describing the anticipation of the CBOT's night bonds session which opened up at 6pm each night: Chicago Girds For Night Shift