SOUDAN, MINN. — It's always 51 degrees, with a quality of darkness rarely experienced, at the bottom-most point of Minnesota's oldest, deepest and richest mine. And after $9.3 million in upgrades, the route to this destination 2,341 feet below the Earth's surface just got smoother.

The Soudan Underground Mine, which was closed to regular tours for two years because of COVID-19 then two more years for repairs, reopened with a full schedule of visitors over Memorial Day weekend. This northeastern Minnesota landmark, attracting 35,000 people a year, tells the story of the immigrants who worked in this mine on the Vermilion Iron Range. It descends half a mile underground and includes a railway ride to a worksite on the 27th level, where miners once trudged through the dark to blast alongside co-workers who spoke different languages.

"It's so fun to be back underground here," said Reed Petersen, a tour guide from nearby Ely. "Not only do we have a lot of fun here, I love sharing the story and giving people in the past credit for the lives they led."

During its closure, upgrades were made to the structure surrounding the site's cage, the elevator that descends at 11 miles per hour at a 78-degree angle into the depths. At one time, this steel enclosure carried more than a dozen workers at a time. Now it feels cozy with eight adult riders on board. Five hundred feet of steel skeletal structure, which had degraded over the years, was rebuilt, and 900 cubic yards of rock and debris removed. Workers were on site 24 hours a day for this tricky job that has just one point of entry: the cage.

The updates might not be visible, but guides say it's now a less jarring 3-minute ride in the cage.

The visitor center, once called the Dry House, has new displays to further tell the story of this mine that was in operation from 1882 to 1962. There is an 8-minute film with the voices of the miners — only men ever worked here — and its relatively cushy conditions. It has been referred to as the "Cadillac of mines." The exhibition room features a large-scale model of what lies beneath, including a re-creation of the 54 miles of tunnels, referred to here as drifts.

The mine closed two weeks before Christmas in the early 1960s — not because it had exhausted the resource, but because other mines in the area had found a way to do it cheaper.

"There is still iron ore here — it was no longer economic to mine," said Sarah Guy-Levar, interpretive supervisor who wore a Soudan Underground Mine T-shirt and hematite earrings for a tour.

Within three years of closing, U.S. Steel sold the site to Minnesota for use as a state park. In recent years, the acreage has expanded and a campground added.

These days, visitors don hard hats, not as much for safety as to get in the mindset of a miner. Above ground, the engine house holds the whirring, vibrating hoist that operates the cage. Its operator communicates with the staff at the cage through coded buzzes. The underground tour includes a nearly mile-long railroad track lit by bare bulbs. Miners once walked the route in the dark, using the steel tracks as a guide to their worksites.

The whole Soudan Underground Mine site is "a geologically complex time capsule revealing human change and technological innovation over time," Guy-Levar said.

While waiting above ground for the cage during a recent tour, Petersen directed visitors to look to the horizon. That, he said, is the Mesabi Iron Range, where there are five active mines.

"The present is at Mesabi Iron Range," he said. "The past is here."

For tour information, go to dnr.state.mn.us/state_parks/lake_vermilion_soudan.