Plitvička jezera

Plitvice is the oldest national park in southeastern Europe — declared on 8 April 1949 — and at close to three hundred square kilometres still Croatia's largest. Almost all of that is beech and fir forest on the karst plateau between the Mala Kapela and Lička Plješivica ranges, holding bears, wolves and lynx. But the park is known for about two square kilometres of it: the chain of sixteen lakes that steps down some hundred and thirty metres over eight kilometres of valley, from Prošćansko at the top to the gorge below Kozjak, and out into the Korana.

The barriers between the lakes are the whole phenomenon, and they are alive. The water arrives supersaturated with dissolved limestone; mosses, algae and bacteria growing in the current draw off carbon dioxide, the calcium carbonate comes out of solution and cements onto the plants, and the plants keep growing through the deposit. The result is travertine — porous, pale, still accreting at something like a centimetre a year — and the dams it builds are therefore not fixed features but a slow-moving construction site. Barriers rise, ponds fill and spill, old dams breach, new ones start. The colours follow the same chemistry: the mineral load and the depth of each basin together decide whether a lake reads turquoise, azure or dark green, and the same lake changes through the year. At the bottom of the sequence the Plitvica stream comes in over the rim in a single fall of seventy-eight metres, Veliki slap, the tallest in the country.

The park was inscribed by UNESCO in 1979, one of the earliest natural sites on the list, and spent 1992 to 1997 on the List of World Heritage in Danger. The war reached it first: the clash at the lakes on Easter Sunday, 31 March 1991, was the first of the Croatian War of Independence to kill anyone, and it killed two — Josip Jović, a special policeman in the Croatian column, whom Croatia commemorates as the war's first casualty, and Rajko Vukadinović on the Krajina Serb side. The area was then held outside Croatian control until 1995. Mines had to be cleared, hotels rebuilt, and the site left the danger list in 1997. What the park now manages is a different pressure: well over a million visitors a year on a network of wooden boardwalks laid directly over the barriers, which is why entry is capped and timed.

What's worth knowing before you go

There are two entrances on the Zagreb–Zadar road, and the buses between the two cities stop at them; the park is roughly two hours from Zagreb and an hour and a half from Zadar. Tickets are sold for timed entry slots and sell out in high season — book online, and take an early or late slot. The boardwalks are one-way and mostly without railings, so the walk is easier than it looks but no place for a pushchair. Autumn is the connoisseur's season for colour, spring for volume of water; winter, when the falls partly freeze and the crowds vanish, is the underrated one.

The detail worth knowing is that most of the park is not the lakes. Ninety-nine per cent of the area is forest that almost nobody walks — including Čorkova uvala, a virgin beech-and-fir stand in the northwest, one of the few genuine old-growth remnants in this part of Europe, and reachable on a marked trail that sees a tiny fraction of the boardwalk traffic.