The Dannemora mines, from the 15th century until 1992 produced ore that was low in phosphorus and sulphur, suitable for making iron well-suited for steel-making. Visitors can take a guided tour of 40 steep-sided open-cast workings, where a feature of particular interest is the building constructed in 1728 by Martin Triewald to house the first Newcomen steam engine to work in Sweden. It operated for only a few years.
At Osterby bruk 4 km E, is the only Walloon forge preserved in Sweden, a late 18th century building that houses two hearths and two water-driven hammers. It stands near to workers’ houses, idyllically ranged along the dam, and to a mansion of the 1730s, occupied for more than a century by the de Geer family, who were of Walloon origin.