Fat biking in the polar vortex in northern Minnesota's Cuyuna area

Steps away from our tiny cabin at True North Basecamp, I stood above a frozen mine-pit lake with my rented fat-tire bike. It was the polar vortex of January 2019, the mercury stubbornly lodged at 10 below zero. Before me, an icy path curved sharply downhill, ending at a narrow wooden plank that spanned the mouth of the rushing Serpent Creek.

My friend Jason whisked by, smoothly rolling down the slope and over the bridge. I gingerly walked my bike down the scree, then slung the frame over my shoulder to cross the open water. If this was typical terrain at Cuyuna Country, my first day at the mountain-biking park was going to be a long one.

But once we were inside the park, Jason and his friend Jared led me onto my first actual trail: the "easy"-rated Drag Line, an immaculately groomed channel in the fresh, deep snow.

We climbed, dipped and twisted on fun but manageable hairpin turns through thick pine woods. My eyes laser-focused on the trail, I felt like I was in a movie where the camera scans over the ground to give the sensation of flying. It was a good enough workout, yet the wide tires on my bike felt like floating on marshmallows. I was instantly immersed in this remote place.

Cuyuna Country State Recreation Area is an anomaly: a state park unit in northern Minnesota devoted to the burgeoning sport of mountain (and fat) biking. Its principal town, Crosby, is also unique in the land of ice fishing and ATVs: an Iron Range community where a genuine bike-based economy has evolved around the park.

True North Basecamp opened on the outskirts of Crosby in 2015, a string of low-frills quarters ingeniously in the style of old mining cabins. When Jason and Jared booked that subzero weekend at the Basecamp, I jumped at the invitation to join in. I returned six months later to experience the opposite weather extreme.

I pulled into Crosby on that cold Friday and immediately headed to Red Raven Bike Cafe, a social hub and the unofficial gateway to the park. A full selection of bikes are available to rent, including Minnesota's own Salsa and Surly brands. The employee easily upsold me to a carbon-fiber Salsa Mukluk with 4-inch studded tires.

Bike obtained, I met up with my hosts at the Basecamp. The sheet metal-clad cabins are modern but spartan, consisting of two bunks, a table and chairs, Wi-Fi, velo-centric wall art, climate control and just enough space for three guys' bikes and gear. The six shacks are lined up above a small mine-pit lake with the industrial-sounding name of Armour #2 Mine.

Cyclists can thank Minnesota's historic mining industry for the park's existence. Though it's quite close to the popular Brainerd Lakes Area, Cuyuna sits at the southwestern end of the storied Iron Range. British pit-lake names like Pennington, Huntington, Portsmouth and Armour #2 suggest that this part of the Range was partly settled by Cornish immigrants.

Mining companies abandoned the area by the 1980s, leaving behind 5,000 acres of scarred terrain, steep bluffs and water-filled pits where an unruly wilderness has clawed back. There was little to do with this difficult real estate other than to forge 40 miles of single-track. Large swaths remain undeveloped and off-limits, amazingly in a world with few frontiers.

Fat biking below zero is an extra challenge, but doable with heavy gear and common sense. We limited rides to about an hour before returning to the cabin for warm food and drink. We hung wet clothing on a line above the wall heater. By night, we headed into town for comfort food at the Iron Range Eatery, followed by beers named for Cuyuna trails — Yawkey Ale, Crusher IPA — at the Cuyuna Brewing Co.

In the morning, we lazed until noon, waiting for the temperature to hit zero before riding. A highlight of Day 2 was a "more difficult"-rated stretch of the Drag Line, which ascends to a vertiginous view of Portsmouth Mine Lake. We followed that with the aptly named Galloping Goose, a rollicking path of rolling ups and downs alongside the narrow pit lakes.

Back at the Red Raven for hot cocoa, we heard employees raving about the "best trail conditions ever." A heavy snowfall had been followed by a fast deep-freeze, resulting in a firm snowpack that was perfect for big tires. My lightweight Salsa Mukluk had been the right call — giving me plenty of power through the snow with less fatigue. Renting a top-end fat bike here a couple times a year is arguably a better value than owning one for upward of $2,000 to $3,000.

In July, I returned to Cuyuna and True North Basecamp with another bike friend, Jim. Temperatures were in the upper 90s with high humidity — a full 100 degrees above my first visit.

The same trails were now an iron-red, rocky clay, swathed in greenery. We rode a few loops before black clouds called us in. Tornado sirens sounded as lodgers watched a fearsome lightning storm on the horizon. A gorgeous sunset followed, with a rainbow directly over the Basecamp — a classic Minnesota summer-cabin moment.

Extreme winter and the height of summer both have their charms at Cuyuna. But next time, I think I'll shoot for some nice, average 50s or 60s.

Mountain bikes and fat bikes are available at Red Raven Bike Cafe from $75 a day. Breakfast is served in the cafe, where employees and regulars discuss trail conditions and park intel. In the summer we watched the Tour de France live on a big screen (2 3rd Av. SW.; 1-218-833-2788 or redraven.bike).

The Iron Range Eatery is the top choice for dinner. The "Range" cooks up pizzas, pastas, burgers and an asiago-encrusted walleye. It's a bit of upscale dining in lake country (6 W. Main St.; 1-218-545-5444 or ironrange.3cheersmn.com).

The atmosphere at the Cuyuna Brewing Co. is spare, but the taproom hits all the craft-beer sweet spots, with IPAs, stouts and lagers (1 E. Main St.; cuyunabrewing.com).

For breakfast, North Country Cafe is a classic greasy spoon, with teen servers delivering pancakes, bacon, eggs and coffee to comfortable booths (12 W. Main St.; 1-218-545-9908).

Cuyuna Country State Recreation Area (dnr.state.mn.us) is two hours north of the Twin Cities outside Crosby, Minn.

True North Basecamp features six basic but modern lakefront cabins from $85 a night. There are also 23 campsites (825 SW. 1st St.; truenorthbase­camp.com).

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