Plitvice Lakes National Park (Nacionalni Park Plitvička Jezera) is located in a mountainous and half-wild corner of Croatia. It has been a park since the 1890s and was a notable tourist attraction in the time of the Yugoslav kingdom. Rebecca West and her husband visited there in 1937 on the tour that became the subject of Black Lamb and Grey Falcon. That book was where I first heard of it. The park was nationalized by Tito’s government in 1949, and 30 years later UNESCO put it on its World Heritage list.

(A brief note about names: Plitivice (‘PLEET-veet-seh’) is the name of the local region (there doesn’t seem to be a town or village with that name) and the lakes (jezera, singular jezero) from which the park takes its name are officially the Plitvička Jezera (PLEET-veech-ka YEZZ-a-ruh), which in English would be something like ‘Plitvitsian Lakes.’)

The Plitvice Lakes
The lakes lie in a deep valley surrounded by mountainous and heavily forested country, where not only foxes and deer, but wolves, bears, wild boars, and lynx can be found. The park is a refuge for a small population of wolves, hunted almost but not quite to extinction, which is beginning to increase again, not through transplants or imports, but on its own native base. Plitvice is also one of the few places in Europe still inhabited by brown bears. (Slovenia also has some, and the rest live in the Carpathian mountains east of Hungary.)

The park includes about 113 square miles, more than three quarters of it forested. The lakes, which attract by far the greatest number of visitors, occupy a comparatively small area in the center, and they are what we had come to see. (The authorities wisely leave the forest alone, and haven’t opened it up to tourism, which doubtless explains why a large and varied animal population still thrives, or at least survives, there.)

In a different environment, Plitvice might be home to a deep canyon with a foaming torrent racing through it, instead of a chain of 16 lakes whose water tumbles from one to the next down what in places looks like a large, uneven stairway. But the water that enters the valley comes from the Dinaric range: high mountains of limestone and dolomite — both of which minerals consist mostly of calcium carbonate, another name for which is chalk. This substance dissolves into and permeates the water of streams that pass over it. One such stream, named Bijela (‘white’), and another named Crna (‘black’), unite, shortly before they reach the valley, into a single river called the Matica (which has several meanings, one given as ‘mainstream,’ so perhaps it’s to be understood as ‘Main Stream’).

In places where the stream hits a rocky obstacle, the calcium carbonate tends to precipitate out of solution and stick to any plants and mosses growing nearby. (At Plitvice this process is aided by the presence of certain species of plants, algae, and even bacteria that thrive in the alkaline environment.) Gradually the plants and moss become coated in a layer of soft, chalky rock. They die, but new shoots keep growing on top, and these in turn attract their own chalky coating. As the pile builds up, it hardens into rock, and eventually forms a solid barrier to the water’s flow. The barrier can add as much as a centimeter to its height each year. That doesn’t sound like fast growth, but in a geological context (which this is) it’s practically warp speed.

The same process — dissolved calcium carbonate precipitating out of solution — is what causes stalactites and stalagmites to grow where water drips in limestone caverns. But in the lightless environment deep underground, with no members of the vegetable kingdom present to assist, stone takes much longer to grow.

Travertine barrier
The carbonate rocks that grow up in places like the Plitvice lakes are called by two names, tufo and travertine, often used interchangeably, although some sources I found on the Web attempt to distinguish them by the way they’re created (hot springs being necessary to make travertine, but not tufo) and others by their characteristics as building material (tufo being lighter and more porous, travertine heavier and more solid). Most descriptions of Plitvice call the rocky barriers that grow up there (without geothermal assistance) travertine, so I’ll stick with that. (The name is Italian, based on the Latin lapis tiburtinus: ‘stone from Tibur’ — a popular building material in ancient Rome. It came from the town about 20 miles from the city whose modern name is Tivoli.)

Over several thousand years, the growth of travertine barriers has slowed the plunging river and broken it up into a chain of 16 lakes, each filled with water that overflows the travertine damming it up and spills into the next lake down. On the map we were given at the park is a chart that shows the altitude of the uppermost lake, Proščansko, where the Matica flows in, as 636m above sea level, and the altitude of the river Korana, flowing out at the end of the chain, as 475m above sea level. So, in a distance of about five miles, the length of the 16-lake chain, the water drops 161m, or about 528 feet — roughly three times the height of Niagara.

More than one downhill path
With the barriers growing continually and unevenly , the water constantly seeks paths to follow downward; even at a centimeter of growth per year, new paths are always being opened. The park’s trails and wooden walkways take visitors past hills down which a couple of dozen small streams may be running, or across water that flows over a grassy travertine barrier and spills several feet, or perhaps just a few inches. In other places (not crossed by walkways) the water falls 20 or 30 feet from one lake to the next. The Big Waterfall, Veliki Slap, is not part of this “stairway;” it’s located where a stream (Plitvica Potok) drops from a high plateau into the deepest part of the gorge.

In the lakes, the varying mineral and algae contents produce sometimes startling shades of green, blue, and all shades between when seen from a distance, especially when the sun is at the right angle. From up close, the water is crystal clear, and a huge population of fish, mostly several varieties of trout, is always in evidence. Catching them is not allowed, so the plump Plitvice trout, whether they know it or not, inhabit a kind of fish paradise.

We also saw a few ducks in the water, and a great variety of wildflowers, none of which we had sufficient knowledge to identify.

The Plitvice Lakes National Park was within the area of the “military frontier” called the Krajina where Serbs settled, by Austrian invitation, in the 17th and 18th centuries, paying for their land with service as Turk-fighters. In the turmoil of the early 1990s, when Yugoslavia was breaking up, the inhabitants of this area rebelled against Croatian rule — the first shots were, in fact, fired within the park — and went on to declare themselves citizens of the independent “Republic of the Serb Krajina.” They hoped that this statelet would eventually become part of a Greater Serbia, but this hope was disappointed, and most Serb residents fled the area when Croatia, having built up its army, reclaimed control of the Krajina in 1995. The national park has been securely Croatian since then. Fortunately for visitors, both sides in the struggle respected the park sufficiently that no perceptible damage seems to have been done. The three hotels that offer lodging to visitors were all built in the days of Communist Yugoslavia, and the Croats are learning (sometimes a bit too gradually) to operate them as if they were no longer a socialist state monopoly. The forests never stopped being green, nor the lakes blue-to-green.