It seems it's an entire complex connected by tunnels.
And a maze at that. I saw what looked like church officials in business attire while I was visiting its food court. They'd come out of some private hallways and closed off areas to go from one area to another, or to have lunch.
The guys in the suits may be busy workers from the COB, but there are also dozens of companies dealing in insurance, banking, maybe gun running to South American countries, etc in the buildings downtown and I'm going to guess they enjoy lunch there and they all will be wearing suits from Mr. Mac, who has a big store there.
Most of the people who go there are sort of dressed up, but there are some tank-top wearing folks too, being watched by indoor drones to make sure they don't do anything unseemly in the Mall O'the Lord.
I saw one slightly older middle-aged man in the Family History Library who looked like a younger version of Thomas Monson. They could've been twinsies, minus the age difference.