There are some special places in this game. Such as Old Tree, a Blood Church, Ruins, Witch Circle or Caves. When you walk on them with one of your units you can get some experience, gold or sometimes an artefact. There are also some special places depending on the story, those are a special hammer or anvil where Dwarvenrock has to go to fulfill the goal of the mission.
When you play through the campaign make sure, that you'll visit as much of these places as possible, you'll need the gold or artefacts that you can get there.