The much anticipated outdoor Winter Classic match-up between the Toronto Maple Leafs and Detroit Red Wings is just under three weeks away and the NHL is busy preparing for the marquee New Year’s Day event. That includes making the perfect sheet of ice.

Just seeing the outdoor ice-pad at the Big House makes Tomas Holmstrom feel like a kid again. The retired Red Wing is getting ready for the Winter Classic alumni game - where he'll play along such hockey greats as Steve Yzerman, Mats Sundin and Wendel Clark.

“Sundin is probably going to skate around out there,” says Holmstrom. “I'm going to have to stop eating, get back in shape, and work on my game."

However, the main event at Michigan Stadium featuring the current Leafs and Wings is just a few weeks away. Now the NHL must convert a football stadium into a larger than life arena.

With all eyes on the stadium- the transition is now underway.

dan craig: "Everybody thinks you can just go out there, put down water, and then we're all good,” says , Dan Craig, NHL Sr. director of facility operations. “If you and I are going for public skating that'd be great, but we have guys making millions of millions of dollars."

Unlike many indoor arenas, it doesn't happen overnight. To make it all possible, a truck arrived in Ann Arbor Friday hauling the world's largest mobile refrigeration unit. The Canadian made and operated ice truck filters 1,400 gal of water onto the eventual playing surface every minute. Operators use state-of-the-art monitoring equipment to make an NHL calibre sheet of ice.

Don Renzulli, Sr. vice president of events for the NHL says it takes about five days to build a good sheet of ice, depending on what Mother Nature throws at you.

"Pittsburgh had rain, and Philly we had nothing but sunshine, so we've kind of gone through all sorts of weather contingencies," says Renzulli.

The real challenge will be in four weeks when the ice truck pulls out of Ann Arbor for its next outdoor game in sunny California.