About four miles south-west of Tavistock, on the Devon bank of the Tamar, Morwellham Quay is the best-preserved Victorian river port in Britain. At its peak in the 1860s it shipped copper, arsenic, and manganese out to the Bristol Channel and the world; today it is an open-air museum run by a charitable trust, with restored cottages, a working assayer's office, a Victorian farm, and a costumed cooper and blacksmith.
The highlight is the tramway ride into the George and Charlotte copper mine — small open carriages trundle through a tunnel cut into the hillside in 1859, with stops where guides explain what miners actually did down here. It takes a full day to do the site properly, and it is genuinely good with children. Allow time for the riverside walk back along the Tamar Valley UNESCO World Heritage area.