Karst by water in stone

18:51, Jan 06 2013
postojna caves
PLAY OF LIGHT: Lights create eerie shadows among the Postojna caves' stalactites and stalagmites.
postojna caves
WATER FEATURE: Millions of years of water seeping through limestone has created amazing landforms.
postojna caves
COLOUR SCHEME: While some of the limestone formations are brilliant white, others in the Postojna cave system were streaked with mineral colours.
plitvice
WALKING ON WATER: Walkways that link the lakes in the Plitvice National Park are the only way to keep one's feet dry in a very watery landscape but they also protect the delicate natural environment.
plitvice
SEEING DOUBLE: Two of the Plitvice lakes, separated by a travertine dam and surrounded by waterfalls.
plitvice
WITH THE FLOW: Water cascading through the Plitvice lake system.

Chemical reactions in rocks don't at first glance seem to have the potential to attract millions of tourists every year but they do precisely that in the rural heartlands of Slovenia and neighbouring Croatia.

The key to the popularity of both Postojna in Slovenia and Plitvice in Croatia is limestone. In fact, the word karst, which is used to describe classic limestone landscapes shaped by water erosion, originates from the Slovenian region of the same name.

The Postojna caves in southern Slovenia have lured a grand total of at least 31 million sightseers during nearly 200 years. They are the most visited caves in Europe and one the largest classic karst cave systems anywhere.

plitvice
WALKING ON WATER: Walkways that link the lakes in the Plitvice National Park are the only way to keep one's feet dry but they also protect the delicate natural environment.

About 2 million years ago, the Pivika River created 20 kilometres of passages. The caves were first explored properly in the early 1800s and the first tours began operating not long after. Back then, the only way for visitors to reach some of the most spectacular caverns and arrays of stalactites and stalagmites was on foot by torchlight.

Today a small electric train transports visitors deep into the caves which are now lit by electricity. Even an early arrival at the cave entrance won't save you from long lines of visitors waiting for the trains. This place has a long and busy season and is not the place to go if you have an aversion to crowds.

The train "carriages" are basic metal seats with no sides and I expected that progress through the tunnels to the starting point for the walking tour would be rather sedate. I was wrong. The train hurtles through the often quite narrow and low passages - this is one place where warnings to keep one's limbs inside the train and for tall people to be prepared to duck actually mean what they say.

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My heart sank when I saw how many people were milling around in the cavernous semi-dark muster point at the end of the train journey. The cave echoed with guides trying to track down their particular language groups and the shouts of cave officials trying vainly to stop people taking flash photographs.

But, amazingly, about 15 minutes after the various groups started to wend their way up the steps of Big Mountain, everyone had become so scattered along the trails that at one point I found myself entirely on my own. Around me were carefully lit towers of stalactites and stalagmites, more spectacular and massive than any others I've seen around the world. There was no sound at all, not even the drip of water . . . and then the lights went out.

Yes, hundreds of people were down here with me, somewhere. But it was still more than a little eerie. I tried to stop myself trying to recall just how many metres I was underground and thus how many tonnes of mountain were above me. The lights came back on just as I was comforting myself with the thought that the various speleothems, some delicate as strands of spaghetti, had been undamaged by even the merest of rockfalls over millions of years.

Apparently, so the cave guides tell you, the lights are turned off deliberately during each visit just to give you a sense of how dark the caves are. Not sure if that's a case of "Yeah right" or not.

Once you lose the crowds and stop worrying about succumbing to mass tourism, the caves are magical. The colours of the limestone vary from brilliant white to striped, marbled forms in pale golds and pinks. While some formations look like crocodiles, vegetables and castles others are just astonishingly beautiful works of nature.

At one point I emerged from a tunnel high above a natural cavern and looking down saw half-a-dozen men wearing long black cloaks, standing quietly behind a rock. They looked decidedly sinister. It turned out they were an a capella choir waiting to perform in a nearby cavern. By the time I descended the steps towards them, they were singing Slovenian folk songs, demonstrating the beautiful acoustics of the cave.

While humans make only fleeting visits, the Postojna cave does have some permanent residents, most notably the weird amphibian known as the "human fish". An aquarium has been installed in one of the caves so visitors can see several specimens of Proteus anguinus. This is a variety of salamander, is totally blind, has a long tail fin and four legs, has gills but also simple lungs for breathing out of water and has rather creepily human-like unpigmented skin. No-one has ever seen the human fish's means of reproduction. The Proteus anguinus in the aquarium lay slug-like along rocks, glowing ghostly white under faint lighting, apparently unconcerned their sex lives remained a mystery.

The walking tour ends in the Conference Hall which is so large it can accommodate up to 10,000 people for musical performances. The trains meet visitors here and propel them back out into the light and the maelstrom of milling crowds, shops and restaurants. It's a bit of a shock to the system.

Across the border in Croatia, limestone is also a star attraction but with a twist. The Plitvice Lakes are one of Croatia's most popular destinations, attracting more than 1.2 million people every year. The lakes are the centrepiece for the country's largest national park, at almost 300 square kilometres.

Although the simple explanation for the formation of the 16 lakes is that they too are manifestations of a karst landscape, the real story is much more complex and fascinating.

The water that flows through this region is retained in the Plitvice lakes because of the creation of travertine dams. Travertine is a variety of limestone deposited by natural springs, especially thermal ones. In Plitvice, the travertine has accumulated over the centuries on top of rock, moss and algae, creating dams which in turn transform into waterfalls as the water levels rise.

If you have visited Pamukkale in Turkey, you will have already encountered travertine in its natural state. However, there's a good chance you will have seen it as cut stone in many parts of the world. The ancient Romans loved its creamy white and tan colours and used it in the Colosseum in Rome, the largest building in the world built primarily of travertine. Michelangelo included travertine in St Peter's Basilica in Rome and it was also used in the Sacre Couer in Paris.

But, back in Plitvice, travertine has created some special features. Mosses and travertine combine to build up walls, which eventually rise above the water surface to create cataracts (from the Greek word meaning "that which collapses") and tall waterfalls (the biggest is the Veliki Slap at 70 metres tall); the two also work together to build caves, tubes and curtains of travertine combined with living moss.

The lakes have been known to local people for thousands of years and have acquired names related to either mythical or real events that have taken place there. There are lakes named after a grandmother, a gypsy and others who have apparently drowned in them (swimming is not permitted in the lakes so there's little chance of anyone else being remembered in this way). Other lakes have descriptive names for the way their waters whirl or boil.

One lake is named after a herd of goats that drowned after trying to escape from a wolf pack. Although wolves in theory still live in the park, this is another fate (along with drowning) that is unlikely to befall visitors nowadays. The forests that surround the lakes are mainly beech and fir, along with many other European tree species such as maples, pines, oaks and elm. Living in this woodland, along with the wolves in the most isolated areas, are bears, wild boar, deer, martens, fox and badger. Rare sightings of lynx and otter have also been reported.

Most visitors walk the circuit around the lower lakes and we were warned that, at times, the route, which includes walkways suspended above the lakes and streams of crystal-clear water, could get very congested.

However, on the autumn day I visited, although the park looked busy to me, our guide expressed her amazement at how quiet it was. What was a bonus for crowd-shy Kiwis was not viewed nearly so positively by locals who rely on tourism for their livelihoods.

Paths led through deciduous forest where leaves were just starting to turn golden and burn orange, to a vantage point overlooking several of the lakes. Because of the geological composition of the area, along with the lakes' varying sizes and depths, the colours are startlingly varied from emerald green to bright turquoise. Each one was different.

As the weather had been dry through summer, the waterfalls that tumble over travertine cliffs through the park were not in full flow but this was still a liquid landscape at ground level.

The paths linking the lakes wound along beside flowing streams, full of lazy fat trout (fishing not permitted); walkways were suspended over a watery world of tiny islands, rivulets and cascades. It was an ever-changing landscape set against the constant sound of gurgling and gushing water . . . geological poetry in motion.

It was a landscape of shadows, and the play of light on water, ripples and reflections glimpsed through sunlit trees. And, thanks to the slight downturn in tourism, it was possible to find a place to sit alone and contemplate the results of an extraordinary union between water, minerals and living plants.

The Timaru Herald