Kozjak

Kozjak is the largest and deepest lake in Plitvice Lakes National Park, located near Plitvica Selo in Croatia. Stretching almost 2.5 km in length, covering roughly 80 hectares and reaching a depth of nearly 47–49 metres, its turquoise surface framed by limestone slopes and dense forest makes it the central and most recognisable feature of the entire sixteen-lake system.

Where exactly is Kozjak located?

The lake sits at an altitude of about 534 metres above sea level and forms the natural boundary between the Upper Lakes and the Lower Lakes. This is precisely where two different geological eras meet — the Triassic dolomites that shape the Upper Lakes and the Cretaceous limestone typical of the Lower Lakes. Because of this central position, most walking trails through the park pass along or across Kozjak at some point.

What can you see around Kozjak?

Kozjak is the only lake in the park open to boat traffic — electric ferries shuttle visitors between piers P1, P2 and P3, linking the Upper and Lower Lakes trails. It is also the only Plitvice lake with an island: the small, tree-covered Štefanija's Island, visible from the ferry deck as it crosses the water.

A striking piece of hidden geology lies beneath the surface: until roughly 400 years ago, two separate lakes occupied the spot where Kozjak now sits, divided by one of the tufa (travertine) barriers so characteristic of Plitvice. That barrier, once about 400 metres wide and 36 metres tall, now rests some 6 metres below the waterline — a vivid reminder of how actively the landscape here keeps reshaping itself as new tufa deposits form.

Where does the name come from?

According to local legend, the name Kozjak comes from twelve young goats that drowned while trying to swim across to the far shore. Passed down through generations of residents in the surrounding villages, this story remains the most widely told explanation for the lake's name.

When is the best time to visit Kozjak?

The lake is striking in every season, though its turquoise colour is most intense in spring and summer, when strong sunlight illuminates the pale limestone lakebed. In autumn, the surrounding forests turn shades of red and gold, creating a vivid contrast with the water. In winter, when temperatures drop below freezing, parts of the lake can partially freeze over and ferry services run on a reduced schedule, so it's worth checking the current sailing times before a winter visit.

Frequently asked questions

Can you take a boat ride on Lake Kozjak? Yes, Kozjak is the only lake in Plitvice Lakes National Park served by tourist electric ferries, connecting piers between the Upper and Lower Lakes.

How big is Lake Kozjak? Kozjak is about 2.5 km long, covers close to 80 hectares and reaches a depth of around 49 metres, making it the largest and deepest lake in the park.

Is there an island on the lake? Yes, Kozjak is the only Plitvice lake with an island — Štefanija's Island — visible from the deck of the passing ferries.

Where exactly is the boundary between the Upper and Lower Lakes? That boundary runs right through Lake Kozjak, which links both lake systems and marks the meeting point of two distinct geological formations within the park.