Plitvice Lakes National Park, some 80km from the Adriatic, is Croatia’s most enticing natural attraction. Like a colossal water garden, this 8km string of sixteen crystal-clear, turquoise lakes descends through some of Europe’s most primeval forests (complete with brown bears, if you know where to look), connected by rushing waterfalls and linked by footpaths, wooden bridges and walkways. Kids love the park, and Plitvice’s limestone geology makes it unique, and has brought it UNESCO World Heritage Site status. As such, visiting is a well-organized affair, with big crowds in the summer. But the lakes have a minor-key majesty that makes the crowds bearable, and out of season they can be relatively quiet. By using the shuttle buses and boats, you can see much of the park in a day, taking the bus to the upper lakes and walking down. Better still, spend a few days here: there’s a cluster of hotels near the middle, and private rooms in nearby villages, meaning you can get up early to enjoy the lakes in all their pristine, untouched glory.
Most buses between Split and Zagreb stop at the Plitvice Lakes. See http://www.np-plitvicka-jezera.hr.