A Classic Polje

A panorama of Planina polje

Polje is a cool word in English language. It is borrowed from Slovene – where it means ‘a field’ – and is a terminus technicus for a ‘karst field’, a large flat-bottomed depression in a limestone area.

Meandering river Unica and the town of Unec beyond

Planina polje is a classic example of this geological formation. A 5 km by 2.5 km flat depression oriented northwest-southeast (a typical Dinaric direction) lies some 40 km southwest from Ljubljana, Slovenia, and is full of wonders.

Planina polje

You can see that this plain is full of meadows and pastures, and there are no villages on it. Such open and flat valleys are quite rare in this part of Slovenia, so why it is not covered with fields and farms? The answer lies in the complex geology and hydrology of Planina polje, of Slovenia, and of Europe.

Unica at the edge of Planina polje

In general, this is all a consequence of African plate crashing into Eiuropean plate, with Adriatic plate and her somewhat erratic movement wreaking havoc on the area between the Adriatic sea and the Alps. One of many faults crisscrossing these lands is the prominent Idrija fault that has its fingers deep in the jam jar of karst fields in Slovenia, Planina polje included.

Idrija fault

From Prezid and Babno polje to Lož and Cerknica with its famous intermittent lake, to Planina polje and beyond all these karst depressions (and narrow valleys between them) lie in a straight line – this is the Idrija fault. Karst depressions – almost every polje in Slovenia – developed in Triassic and Jurassic limestone mountains along that fault, and waters filled their bottoms with impermeable sediments, enabling rivers and intermittent lakes flowing across them.

Meandering river Unica

An interesting thing is that all these poljes from Prezid to Planina are sharing only one river. It is a wondrous river of seven names that first springs up as Trbuhovica near Prezid, and disappears underground at Babno polje. The river emerges again at Lož polje as Obrh, sinks into the cave Golobina, springs again at the edge of Cerknica intermittent lake – this time it’s named Stržen – only to go back into the ground and again into the light as Rak in Rakov Škocjan valley, disappearing yet again in Tkalca (Weaver’s) cave, flowing underground and meeting Pivka river in a magnificent underground confluence of Planina cave, coming from it onto Planina polje as Unica river, sinking for the last time at the northwestern end of Planina polje, to finally emerge at the edge of Ljubljana Marshes as Ljubljanica. A fantastic journey, right!

Planina polje from a kite

Unica that gently meanders from Planina cave to the sinkholes in the northwest is responsible for the conspicuous absence of fields and farms at Planina polje … when the melting snow and spring rains – and occasionally autumn rains – send millions of cubic meters of water down the catchments of Trbuhovica, Obrh, Stržen, Rak, and Pivka rivers, Unica blasts from the cave with enormous power, speeds across the plain and arrives to the sinkholes way too enormous for the porous limestone to gulp it all. The waters spill over and Planina polje turns into a beautiful lake.

Meandering river Unica

There are no crops that can thrive in these conditions of unpredictable flooding and periods of drought. The villages are clinging to the edge of Planina polje, and wet meadows are used for grazing and cutting hay. Horses – a remnant of times before the Southern Railway when Planina was an important stop on the Trieste – Ljubljana – Vienna coach route – and cattle kinda like the place, and even they look tired of the moist ground.

Kite aerial view across Unica towards the town of Planina

A fantastic cave awaits an intrepid spelunker, a Medieval tower a history buff … a treasure trove for a botanist and wild animals lover, a fairytale spot for a fly fisherman, a top location for a kite aerial photographer … Planina polje is a Ramsar wetland site, a protected landscape park and a Natura 2000 area. It is a truly exceptional piece of nature that presents a different face every visit – now it’s a lake, now it’s a lush meadow landscape bathig in the sun, now it is a snow covered plain with a green river cutting through the immense white. Planina polje never ceases to amaze and thanks to being slightly off the beaten trail it is devoid of crowds, peaceful and tranquil. If you visit Slovenia and have a day off, don’t forget to visit this gem!

Kites dancing above Planina polje - as seen from a kite

Kite aerial photos shot with Nikon P330 on The Sumo Fighter rokkaku kite made by Dr.agon kites.

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