13 And it came to pass that he caused many buildings to be built in the land Shilom; and he caused a great tower to be built on the hill north of the land Shilom, which had been a resort for the children of Nephi at the time they fled out of the land;
This detail is internally consistent with another mention of that same area:
4 And now, they knew not the course they should travel in the wilderness to go up to the land of Lehi-Nephi; therefore they wandered many days in the wilderness, even forty days did they wander.
5 And when they had wandered forty days they came to a hill, which is north of the land of Shilom, and there they pitched their tents. (Mosiah 7)
The area north of the hill that the people following Mosiah came to as they fled to Zarahemla is the same place the wandering Nephites ended up when they came in search of Zeniff's group.
Something about the natural geography of that area brought both groups to the same spot.