Even if you’re reluctant to take the plunge, there's plenty to see and do above ground at this vast mine complex 2km south of the town centre. Underground, a staggering 20km of caverns and shafts contain galleries, artefacts and the world's deepest hotel suite! Tours go 60m or 150m deep into the mines, every half-hour from 11am to 3pm. Note: you'll need to walk down and up about 300 steps and it's freezing down there, so descent isn't for everyone.
Be sure to bring warm clothes if you're planning to go down, and book your tickets in advance on the excellent, easy to understand, website.
It's hard to believe that the working mine closed as far back as 1908! The museum village above ground contains artists’ workshops, a restaurant (11am to 4pm, May to September, daily lunch 85kr) and a museum (free admission), with displays including a timeline of Swedish mining history and the barrel that was used to lower King Karl XI into the depths for his royal visit in 1687. You can also stay above (or below!) ground at the Gruvgården B&B.
Both village and mine are off the Västerås road. It’s a pretty walk along the Gröna Gången (Green Walk), which takes you southwest via the parks and the Mellandammen pond at Sofielund. Bring a camera – the weird landscape of mysterious, purpose-built structures in the area occasionally sprouts chimneys or falls away into deep holes.