East Campus had some coed floors with 5 bathrooms. They were originally all coed bathrooms. Then at least one bathroom was designated female only. There was also a larger bathroom with two showers in a common area.
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I used to go to a Holiday Spa that was so small (how small was it?) that it only had one locker room. They would alternate men and women each day and night, so Monday would be men in the day and women at night, then Tuesday would be women in the day and men at night. Many of the older guys would swim in the nude.
IIRC, it was Friday that they allowed everyone in. The women had two rows of lockers, the men had two rows of lockers.
And everyone used the same showers, which had shower curtains.
Ah, yes, that rings a bell. I didn't attend MIT myself; I lived in Philly and went to Drexel. But my buddy from high school was at MIT and I drove up to visit a few times over the years. Interesting times.