Cliché? Only within a certain body of gamers. It's a new cliché to me :-)

The secret doesn't have to be secret from us, or necessarily from your erstwhile mapper. If you are mapping in story terms as the omniscient narrator, you can lay out quite clearly things like effective radius of control, source of life-giving radionuclides, or what-have-you. If you're mapping first-person as someone in-story, you could be an outside researcher figuring out why people are drawn to the mall, or you could be a wholly-controlled cartographer showing the boundaries beyond which your growing tribe feels acute pain and overwhelming urges to come home....

The circle of bluegrass players was doing as such do, passing around the 'lead' with a nod or a raised chin. The newbie on the edge was hesitant, till one of the oldest asked him to start something. He hesitated, embarrassed at how little he knew - then said he could play Orange Blossom Special if somebody else would lead. A brash young technical expert harshly crowed "THAT old cliché?" Before the noob could totally wilt the old real bluegrass master spoke back up and said "If'n you caint play an oldie somehow new, ye ain't half tryin'." He then lifted his fiddle and leaned in on the whistle of that train, at no more than twenty miles an hour. The new player was able to fit his guitar in the space between the rails, and all was well.

I bet your mall will be different from any sentient-plant-ruled mall anywhere :-).