But it was Wired — hiring the services of the Piper Cub-flying photographer who shot the first aerial photos of Apple’s data center — that showed us what it looks like.

What you’re seeing above is a cluster of servers about one twenty-fourth the size of Apple’s main 500,000 square foot facility. The structures jutting out either side like caterpillar legs are air-conditioning units sucking in hot air and blowing back cold through those J-shaped ducts. The trailers on the left are portable power units to back-up the 100-acre farm of solar collectors Apple is planting across the road.

According to the construction permit filed with Catawba County by Apple — and discovered by the Hickory Daily Record — the 21,000 square foot building has 11 rooms (including one unisex bathroom), 22 air conditioners, 14 humidifiers, 5 fans and two “man trap” security doors. Cost: About $1.9 million.

And what is its purpose?

Some have speculated that it would run iCloud in an emergency should the main data center ever go down. But Apple told county officials it was a “tactical” data center, which in the server business is a term of art.

Dell (DELL), for example, makes a tactical data center it sells to the military. It’s a green cabinet that can be loaded by fork-lift into a helicopter for deployment in war zones.

Unless you count its multi-pronged legal campaign against Google’s (GOOG) Android, Apple doesn’t fight a lot of wars, and what it is building in Maiden is clearly several orders of magnitude bigger than Dell’s portable cabinets.

My guess is that Apple’s new facility will serve a need spelled out two years ago by ZDNet‘s Jason Perlow in a post in which he suggested some smart uses for the company’s huge cash hoard — then $50 billion, now $117 billion:

“As the company grows,” he wrote, “it’s going to need to expand its content distribution infrastructure. That means in order to get things like huge, bandwidth-hungry HD movies downloaded to iTunes or even streamed directly to Apple TVs and iPads, it is going to have to get that content in close proximity to the ISPs that provide broadband service to consumers as well to the Tier 1 providers that provide backhaul services to wireless carriers that sell the iPhone and iPad 3G worldwide.”

One giant server farm, he explains, no matter how big, won’t do the job. It can’t solve the latency issues that slow downloads to a crawl when millions of customers try to grab the same multi-gigabyte files — like OS X Mountain Lion — the same time.

For more than a decade, Apple has relied on Akamai’s (AKAM) network of distributed servers to spread those loads — something the Cambridge, Mass.-based company does very well.

But even Akamai can’t handle the crush of Apple enthusiasts desperate to upgrade.

Moreover, it’s not in Apple’s nature to depend on another company for so strategic a technology.

So it wouldn’t surprise me a bit if the structure shown above is the prototype of a new generation of million-dollar data centers designed for deployment near major Internet service providers, just as Perlow suggested, to support and perhaps ultimately replace the $500 million facility a few yards away.

Leave it to Apple to disrupt its own state-of-the-art server farm.

Below: Wired’s annotated overview of the Maiden, N.C., facility. More photos here.