More than 80-feet below Judd Avenue in Grand Rapids there are six miles of naturally formed tunnels.

The tunnels used to house miners in search of gypsum deposits, but now, it's home to things like city records, produce and thousands of barrels of beer.

The mine went bankrupt in 1943. It's new owner took over several years in hopes of making it a site for furniture manufacturing, according to the Michigan Natural Storage website. But when the furniture endeavored flopped, the owner had a new idea: temperature controlled storage.

It wasn't until 2006, when Founders brought all 28 of their Kentucky Breakfast Stout barrels over to the space.

"It started with two barrels, and then four...and by the time we had 24 barrels we were like 'what are we going to do with all these?'" Kosmicki said.

And, now.

"There's 9,239 of 'em," said Jeremy Kosmicki, brewmaster at Founders Brewing Co.,

Jeremy Kosmicki, brewmaster at Founders Brewing Co., walks through the old gypsum mines where the brewery stores many of their barrel aged beers.

Bourbon barrels, and even some gin, tequila and scotch barrels filled with both old and new Founders recipes are aged in the 45-degree cooler.

Kosmicki, who started out on the packaging line at Founders (which only used to run about twice a week), is now the recipe mastermind behind the brewery's most popular beers.

He said he has put almost every beer they've ever made into a barrel. For him, experimenting is key.

"The only way to figure out if it's going to work is to put something in there and see," said Kosmicki.

The Founders Barrel Aged Series will have four new releases during 2018 with the first one coming out in May.

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