Like a tale about three sisters, each one more beautiful than the next, this park has over a dozen lakes, each one lower than the last, linked by endless waterfalls.
You should be given a map at the Park entrance. There are paths everywhere and a "train" and two boats provide leisurely transport within the park (covered by your park entrance) but you may still want to leave any push chairs behind. It may be a little cooler than Zagreb but not too different.
It's a few hours from Zagreb. There are regular bus/coaches from the central bus station. There are no trains from Zagreb to Plitvice.
Plitvice Lakes National Park - official site
Plitvice Lakes - from the Croatian Tourist Board
Plitvice Lakes - from dalmacija.net
Origins and history of Plitvice
Flora and fauna of Plitvice