Artist drawing of the toliets in the Theatre of Pompey in Rome. This was a 100 seat toliet complex.
Seats at the Roman Port City of Osta, Italy.
Toilets from Roman controled Corinth, Greece
Sewer drainage line at the baths in Wroexeter, England
Romans were very proud of their puplic toilets that used running water to flush away the human waste into sewers. As you can see in the artists drawing, the seats were open to each other to encourage communication among the users. These were unisex toilets so your neighbor to one side might be male and female to the other. Toilet paper was unknown, instead you used a sponge on a stick that you dipped in fresh water, cleaned your self and replaced for the next user.
In the last picture I find it very interesting that 1900 years ago the Romans at Wroxeter had flushing toilets while those visiting the historic site today have to use the port-a-pot seen in the background.