The Plitvice Lakes National Park (Plitvička Jezera) is a beautiful UNESCO protected area with a total of 16 interconnected lakes in Croatia. The water is very clear and from farther away glows from blue to greener colors. Besides the water color, what makes the area spectacular is the difference in altitude of the lakes so that they are laid out as a stair case with beautiful waterfalls between them.
The park is divided into two groups of lakes around the largest one, lake Kozjak. The 12 upper lakes (Gornja jezera) are easily accessible with a 2 minute ferry ride. A path leads you around the lakes and pass many spectacular sights and waterfalls since many lakes are pretty small.
This is also by far the most crowded area of the park which can be a bit too much if you happen to arrive at the same time as tour groups from Zagreb or from the coast. We booked a night in one of the bigger hotels from the times of the USSR to enjoy the lesser crowded evenings and afternoons. However, when we started the trail after our arrival in the afternoon it was one big line of people with lots of traffic jams at popular photo spots. It was still nice but so hectic that it was hard to enjoy for what it was. This changed luckily drastically on the return hike when most groups have left and the paths were almost completely deserted. We had the same experience in the morning, so my advice is to stay for a night and explore the park in the off season hours. The hotels are also able to extend your day ticket for the next day which is nice so that you can visit both sections (upper and lower lakes) at different days (lots of walking).
After exploring the closer waterfalls of the upper lakes again in the morning, we took the longer ferry ride (15 minutes) to the lower lakes (Donja jezera). While you walk mostly next to the shore at the upper lakes, most paths on the lower lakes take you up the surrounding hills that allows great views into the canyon-like lower lakes.
The lower lakes also feature the large waterfalls (Veliki slap), as the name says the largest waterfalls of the park with a height of 78 meters. Here is a picture of the falls from close by.
The only drawback on a hot summer day is that there is strictly no swimming. But with an annual amount of more than 1 million visitors, this is necessary to preserve the lakes and the water quality and thus not hard to understand and respect. We left in the afternoon towards the coast to finally cool off in the sea.