In Mosiah 1:18 we read:
And now, it came to pass that Mosiah went and did as his father had commanded him, and proclaimed unto all the people who were in the land of Zarahemla that thereby they might gather themselves together, to go up to the temple to hear the words which his father should speak unto them.
Stephen D. Ricks notes the significance of the location chosen by King Benjamin::
A society’s most sacred spot is the location where the holy act of royal coronation takes place. For Israel, the temple was that site. So we read that, during his coronation, Joash stood “by a pillar [of the temple], as the manner was” (2 Kings 11:14). However, the temple had not been built when Solomon became king, so he was crowned at Gihon (see 1 Kings 1:45). Gihon was made sacred by the presence of the Ark of the Covenant (which contained the sacred objects from Moses’ day) within the special tabernacle that David had made to shelter it. The priest Zadok took “out of the tabernacle” the horn containing oil, from which he anointed Solomon (1 Kings 1:39). In the Nephite case, the temple at Zarahemla was the site chosen for Benjamin’s address to the people and for the consecration of his son Mosiah as king (see Mosiah 1:18)– Stephen D. Ricks, “King, Coronation, and Covenant in Mosiah 1–6,” in Rediscovering the Book of Mormon, edited by John L. Sorenson and Melvin J. Thorne (Salt Lake City, Utah: Deseret Book Co.; Provo, Utah: Foundation for Ancient Research and Mormon Studies, 1991), Chapter 19
How was Joseph Smith able to get all these small details correct?