Late Night

Hank Stuever: Looking for something to do in Kansas on a sunny Saturday last spring, I chose darkness, and drove to Hutchinson (pop. 42,000) to take a tour of the subterranean salt mines at the edge of town. At a museum, you buy a ticket and ride a large, clanky freight elevator 650 feet underground, into pitch black.

There was no crowd. I had the vast, dimly lit caverns almost to myself — and what a place. A long series of featureless gray tunnels gave up millions of tons of rock salt over the last century (and still do), excavated over decades by laborious room-and-pillar mining techniques. Down there, it's always dry and a perfect 67 degrees. You take a little train through the dark and learn a lot about drilling and geology.

The most interesting part of the mines, however, is entirely off limits. Nearly 2 million square feet of tunneled rooms have been profitably repurposed for film and document storage. Hollywood rents some of the space and so does the government. Shelf after shelf of original negatives of movies and old TV shows are kept here below the prairie, safe from almost any apocalyptic or meteorological scenario you can imagine, secure even from the hungry eyes of YouTube and Hulu.

Included in this stash are more than 4,000 episodes of the legendary "Tonight Show Starring Johnny Carson." His farewell episode aired 20 years ago this month. At some point, the entire archive of tapes — the rights to which Carson fully acquired in one of his many highly publicized contract renegotiations with NBC — came here for eternal rest. Except for the standard clips you see from time to time (one of Joan Embery's small zoo critters urinating on Johnny's head; various Carnac the Magnificent routines) and the retrospectiveDVD sets that come and go, the real breadth and achievement of the Carson era is difficult to grasp if you didn't live through it.