Salt was mined here already in the 5th millennium BC. The wealth of the local population was based on salt, which traded with both the Baltic and the Mediterranean countries. An entire cultural era has been named for this small Hallstatt old town.
For me, the charm of Hallstatt is a combination of antiquity, beauty and the feeling of isolation from the whole world that arises there. However you can feel that, only if you accomodate in the town or come in the unpopular season. The region is worth a stopover for a at least few days (better 1 week). One-day exursion might be only disappointment – too short and soooo many people.