At Green Lake near Spicer, workers are busy harvesting a cold crop — big blocks of ice.

The blocks will be used to build the ice palace for the St. Paul Winter Carnival later this month. Ice harvesting is a long tradition in Spicer, Minn., that dates back nearly a century.

Temperatures in the central Minnesota town didn't get much above zero Wednesday. That's uncomfortably cold weather to be working outdoors. But it's great for making ice.

Cool castles: Ice palaces of the Winter Carnival

On Green Lake, which borders the east side of town, crews will spend the next several days cutting blocks of ice that weigh nearly 600 pounds each. They need about 3,700 blocks to build the palace to be the centerpiece of the St. Paul Winter Carnival.

It's a precise process: First, they dust off the ice with a sweeping machine. Then, they use a specialized saw to score the ice into carefully measured sections.

"See, right now we're scoring down about 12 inches. And the ice is 16, so we're leaving four inches. And that's what carries us the whole time while we're working on it," said Mike Lint who works for Wee Kut, a local company that's been cutting ice for 30 years.

A volunteer uses an ice pick to push blocks of ice down a pre-cut channel leading to a conveyor belt. Evan Frost | MPR News

Workers cut away three sides of the ice float, making room around it. Then they use a chiseling tool to break off the blocks.

The workers push the blocks through a channel they cut earlier all the way to shore. A conveyor belt lifts the blocks onto dry land, where they are loaded into wooden pallets.

"In total we're going to do 4,000 which will be about 60 loads going into St. Paul from here to Rice Park," said Mike Gutknecht who works for Park Construction of Minneapolis, the general contractor for the project. It will take five to seven days to truck all this ice to St. Paul, he said.

A nearly 600 lb. ice blocks slides down a wooden ramp after being carried up a conveyor belt. Evan Frost | MPR News

Gutknecht said Green Lake is known for freezing early and producing thick, clear ice.

"When we go back to St. Paul and shine the lights through it, you can get all the visual effects," Gutknecht said. "You'll get milky ice and that type of ice, but out here it is crystal clear and it's got a blue tinge to it. It's really beautiful."

The last time ice was harvested from Green Lake for the St. Paul palace was 1992.

"We make good ice. That's why St. Paul wanted it," said Spicer's mayor, Denny Baker. Baker added that this year's ice palace will get extra attention with Minneapolis hosting the Super Bowl.

A Wee Kut Ice worker uses a custom made ice cutter, formerly a cement cutter, to score a 12-inch deep cut in the sheet of ice in Green Lake. Evan Frost | MPR News

"Most people you know have never seen a block of ice," Baker said. "And then to see what you can build with it and how you can build a structure — that will be amazing. It will be fun for them."

Ice harvesting on Green Lake dates back to the 1930s, when local companies used to cut it and deliver it to resorts to use throughout the summer.

Many of the tools used today haven't changed much since then.

The splitter bar is the same ones they used in the '30s, Lint said, and the wooden-sided conveyor belt used to hoist the ice blocks was built around 1941. Without it, it would be almost impossible to get the ice onto shore.

A wood-sided conveyor belt sits on the edge of Green Lake, ready to carry 600-lb. ice blocks. Mike Lint of Wee Kut Ice says it was built around 1941. Evan Frost | MPR News

"Each one of those blocks weigh close to 600 pounds apiece so you can imagine the amount of weight," he said.

A few old timers turn out every year to help out with the ice harvest. Brothers Bill and Jim Doty are both in their mid-70s. Bill Doty said he doesn't mind the cold.

"You dress for it, you know," Doty said. "In fact, I almost got too much clothes on if you can believe it."

A Park Construction worker receives a block of ice as it slides down a wooden ramp and directs it toward a waiting wooden pallet. Evan Frost | MPR News

Some years the weather hasn't gotten cold enough to make thick ice by January. Gutknecht said they were hoping for at least 12 inches, and they have at least that.

"(Cold weather) is a very good thing for us," Gutknecht said. "Two weeks ago we were worried it was only 8 inches thick out here so we were thinking about having to go to a different lake which is further away. So this worked out great for us."

Once all this ice is in St. Paul, construction of the 70-foot-tall ice palace will begin. The whole thing has to be done by Jan. 25, when the Winter Carnival begins.