Throughout the Book of Mormon we have only hints as to the extent of the population of which we are dealing. The fact that Mosiah could send out messengers to gather the people together "at the temple" suggests a somewhat limited population concentrated fairly close to the city of Zarahemla. Later on, however, we have references to distant cities which suggests that a "conference" may have only included the main body of the people near Zarahemla, just as Church conferences in pioneer days drew most of its attendance from the Wasatch front.
The fact that the people camped around the temple with their families tells us that they had constructed a temple in Zarahemla similar to the one which Nephi had built in the land of Nephi. We also remind ourselves that these temples were not large and only sacred ceremonies were performed by the priests inside the temple. Meetings were held outside the temples in "courtyards." But in this case where each family set up a separate tent it must have spread over a large area that we might call a "temple square."