Lake Vermilion-Soudan Underground Mine State Park: Go down the mine shaft in a cage via a 90-year-old hoist system at this "Cadillac of Mines" on the Iron Range. The ride takes you a half-mile underground and three-fourths of a mile into a tunnel to view the working conditions of miners until 1962, when the mine closed. Summer tours, one and a half hours, run daily from Memorial Day through September, and weekends in October. College students lead tours of the physics lab, where scientists search for "missing" particles called dark matter. Adults $12, children under 13 $7, children under 5 free. 1302 McKinley Park Rd., Soudan. Reserve at 1-866-857-2757 or dnr.state.mn.us.
Hull-Rust-Mahoning Mine View and Mineview in the Sky: At two outlooks, one in Hibbing and one in Virginia, you can walk to the edges of massive man-made canyons and experience the vertigo of pressing up against the chain-link fence and peering down a 200-foot drop. In Hibbing, children can climb on giant equipment, including trucks the size of a modest cabin and 12-foot-tall tires. The gift shop is a quirky ode to the industry, with "Keep on Trucking" T-shirts and tiny crystals for sale. A similar Shop at the Top at the Virginia overlook is slated to close at the end of next month; the visitors' center stands on ore-rich ground that is next in line for mining. Hull-Rust-Mahoning Mineview, 401 Penobscot Rd., Hibbing, is open 9 a.m. to 5 p.m. daily mid-May to mid-September. Mineview in the Sky, Virginia, is open 9 a.m. to 5 p.m. daily through Sept. 30. Free. ironrange.org.
Hibbing Taconite Tour: The mining company offers a tour of its active mine via the Minnesota Discovery Center in Chisholm. Hard hats and safety goggles are required on this school-bus tour, which makes a brief stop to watch those monster trucks in action. The electric vehicles sound like airplanes coming in for landing as they roll past to a loader that dumps some 240 tons of black rock in the hauler, to the tune of fireworks. The explosive sound strikes again when the same trucks dump what looks like crushed Oreos into a seven-story-deep hole, where the rocks are ground into a fine powder before being reformatted into magnetic pellets — the clay of steel artists. The Thursday tours are finished for this year, but will reopen next June. $13, ages 10 and up only. Reservations are recommended. Information at 1-218-254-7959 and mndiscoverycenter.com.
Hill Annex Mine State Park: Take a bus journey around an open pit mine that closed 37 years ago, rather abruptly. Everything was left intact mid-shift, including the raw material that had been rolling on outdoor conveyor belts. It's all still there, rusting, like a graveyard monument to the industry. Marine fossils, formed here in the days when the area was under water, can be discovered and taken home on an archaeological tour. Both tours, each one and a half hours, are offered on Fridays and Saturdays between Memorial Day and Labor Day. $10 adults, $6 children 12 and under, free children 5 and under. Hwy. 169, Calumet. Reservations at 1-218-247-7215 or dnr.state.mn.us.
Forestville/Mystery Cave State Park: Knowledgeable rangers escort visitors underground to this massive network of corridors. The Scenic Tour, at a quick one hour, introduces some of the cave's most dazzling features and is stroller- and wheelchair-accessible. A one-hour Flashlight Tour and a two-hour Geology Tour take visitors on more rugged journeys into another part of the cave. Adventurers can take the four-hour Wild Caving Tour, done mostly on hands and knees. Times and prices vary. Tours run Memorial Day through Labor Day. Information at 1-866-857-2757 or dnr.state.mn.us.
Niagara Cave: Guides take a constant stream of visitors into this popular cave on fast tours through breathtaking natural architecture. In some places, the cave ceiling soars 200 feet, while the walls shrink to a width just big enough for humans to traipse through. Lights go out in the soaring, swirling Stalactite Room. In peak summer season, tours begin every few minutes, daily 9:30 a.m. to 5:30 p.m. The schedule changes in September. $14 adults, $8 children 12 and under, free children 3 and under. On Saturday nights, take the tour by lantern. $16. 29842 County Rd. 30, Harmony. Information at 1-507-886-6606 or niagaracave.com.