Ice castle built in busy parking lot in Minnesota

>> what's the secret to making the perfect ice castle ? nbc's kevin tibbles found out during a recent trip to minneapolis .

>> reporter: a cavernous christmas palace, glatial caves all created from solid ice, not the north pole but in a parking lot next to the mall of america in minneapolis . kids must love it in here.

>> yeah, they do. they do. it's like a big playground of ice.

>> reporter: the ornate craft craftsmanship, californian with ice in his veins. he has been out in the elements no matter how frigid, turning single icicles into works of beauty. there's no wood, no concrete, no steel involved.

>> we set it up and run water and mother nature does the growing during the nighttime.

>> first he has to groet icicles. so he has an ice farm, of course.

>> they come off nicely off these racks. that's exactly what we want.

>> getting down is even icier. latest crop has been transported to the top where, one by one, christiansen builds his castle. he will have frozen some 4 million gallons of water by the time this is done and that is a lot of ice koocubes.

>> some would prefer just to have the ice in their glass.

>> we could fill a lot of glasses.

>> reporter: how come it's all blue?

>> the thicker the ice, the bluer it gets because ice absorbs water and ice absorbs all the colors of the light except for blue and that's what comes out.

>> reporter: but at night, the colors come alive. there are hundreds of lights embedded in the ice, transforming the castle into something warm and magical.

>> it's really beautiful. it's like sculptures.

>> reporter: but to really warm up, visitors stop by the fire pit to help regain the feeling in their extremities.

>> it is pretty awesome.

>> it's really magical. it's minnesota winter.

>> reporter: how how is brent christiansen ever going to warm up? where are you going after this?

>> kuawi.

>> sooner or later , it's all going to melt. kevin tibbles, nbc news, minneapolis .