Some lakes like to play hide and seek and this one is one of the largest of its kind in Europe.

Lake Cerknica is the largest Slovenian lake, but only when it’s actually there. It is an intermittent lake, spanning over almost 30 square kilometers when it’s full, which makes it one of the largest intermittent lakes in Europe. Lake Cerknica is located in southwestern Slovenia, next to Cerknica town, and spreads across the Cerknica plain (yes, I know, very imaginative names).

Intermittent lakes are lakes which dry out and disappear for a certain part of the year due to various reasons (like Grüner See in Austria, which disappears in the winter. In the case of lake Cerknica, the water stays for about 8 months of the year and drains out during the warmer months, because the lake is situated on a karst plain. Karst is both the name of a geographical region between the Trieste gulf and the Vipava valley and a geological phenomenon in our part of the world. In terms of Geology, karst is a rocky, barren terrain full of sinkholes, underground caves and rivers. It is the result of rivers and rainfall eroding the soluble limestone (calcium carbonate) ground over hundreds of years, which created some of the most amazing caves and geological formations in the world (for example, the Slovenian Škocjan caves are on the UNESCO World heritage list), as well as areas like lake Cerknica.

Impressions of lake Cerknica

So, as I said, lake Cerknica is sitting on top a karst plain, which basically resembles a Swiss cheese with lots of holes, called griddle sinkholes. Since my boyfriend and I were there in May 2020, the lake was about halfway there and we could see both the water and the griddle sinkholes on the drier part of the lake. It is actually more interesting to see the lake half-dry than full, because the sinkhole area almost looks like a weird lunar landscape and it’s possible to walk across the lake bed. You can see me standing under the waterline in one of the photos below and I’ll tell you I had a quite bit of trouble getting this photo, because the ground down in sinkhole valley was super soggy, creating prime class shoe-sucking mud.

Normally the lake fills up in 2-3 days during heavy rainfall in autumn and is also fed Cerkniščica stream and snow melt in the spring, as well as underground waters from the nearby Bloke and Vid plateaus, Javorniki hills and Lož valley. Those water burst out of the underground in springs like the Suhadolca spring in the last two photos below when there is too much water in the underground rivers during the wet season. The draining is a slower process, as it takes about 3-4 weeks for the lake to completely dry out and all of the water drains underground through the sinkholes, making the Cerknica plain a true karst plain.

Naturally, the most distinct sinkholes have old-school Slovenian names like Vodonos (water bringer) and lake Cerknica has been on the European map since the 15th century. The vanishing lake phenomena was first researched by the famous Slovenian (well, Carniolan) natural historian J. W. Valvasor, who established karst as a type of terrain based on what he found at lake Cerknica and today the term karst is used to describe other limestone areas of the same kind, like the ones in France and China, so lake Cerknica is actually quite famous around the world.

Griddle sinkholes and Suhadolca spring

Of course, the same man also documented the local witches’ gatherings at Slivnica, the large hill overlooking lake Cerknica that you can see on all the photos. Mount Slivnica (1114 m) was supposedly the home of the local witch coven, led by Uršula, the famous Cerknica witch, which still makes an appearance during Pust (Carnival) time. According to the locals and Valvasor, the witches brewing potions in their cave right under the peak of Slivnica (in Coprniška jama), were to blame for the frequent storms near Cerknica. Well, the storms are still there, but the cave is absolutely witch-free, so Slivnica makes for quite a nice and easy hike if you want to see lake Cerknica from above. The trail to Slivnica starts in Cerknica town, is well marked, takes about 1.5h to the top (500 m of height difference altogether) and there’s a mountain lodge with food at the top. However, if hiking is not your thing, lake Cerknica is best explored on foot or by bike.

Mt. Slivnica

Exploring lake Cerknica: I recommend starting at the Dolenje jezero village for easy access to the lake – there’s a free parking lot, a cafe and a small regional museum about the lake. There are many marked trails leading around the perimeter of the lake (depending on its state of course) and you can choose follow a specific one or adjust course with each new trail marking and get lost in the woods as we did. The main trail around the lake starts at the parking lot in the form of a wide unpaved road and leads to the Otok (island) village past the ruins of castle Karlovec (here’s a post describing the main trail in more detail). Castle Karlovec also plays a part in the local Romeo and Juliet legend about the lake, which explained why it tends to disappear in somewhat less scientific terms than Valvasor. Also, if you want to see the griddle sinkholes during the dry season, then head right from the parking lot – they’re behind the cafe across from the parking lot.

Anyhow, we followed the main trail for a while and found a burnt cabin on a hill nearby, then followed the one to the Suhadolca spring for a while.

Burnt cabin

After we found the spring we just walked across the lake bed until we reached the sinkholes and had a picnic with one of my #cookathome meals. This time it was roasted salmon and quinoa salad with radishes, pickled onions, spring onions, avocado, apples, dill, safflower, olive oil and leftover pickle brine (I like to use all of my food scraps – here are some tips on how to turn them into food). Since we’re not environmental pigs, we brought our own reusable cutlery and didn’t leave any trash behind, so please, don’t leave yours lying around in nature. 🙂

As you might imagine, the area was teeming with wildlife and there were some huge brown beetles flying around our picnic spot. Luckily they weren’t very interested in our food, because I personally only like bug when they practice social distancing with me. Lake Cerknica is famous for its biodiversity, particularly in bird species, which is why it is also a Natura 2000 protected nature area and part of the Notrajnska regional park. Since we were there in spring, the entire Cerknica plain was in bloom and I can honestly say I’ve never seen such giant Ranunculus flowers anywhere. There were also plenty of strawberries and nettles in the meadows around the trails, giant water lilies in the lake and an awesome tree mushroom somewhere by the trail. You can see some of them in the gallery below, but the flowering plain really is a sight best enjoyed in person.

Nature shots

In addition to lake Cerknica in whatever state it may be, you can also visit a smaller, but permanent, lake Bloke, and some other pretty awesome nearby attractions like the Cross cave (an underground Karst cave system with 22 lakes that I really want to visit soon), which I’ve already listed in the lake Bloke post. After reading these two posts and checking out this Cross cave video, I think you should be about ready to hit the road and head to southwestern Slovenia as soon as this coronavirus madness is done, and I say go for it!