Bohinj mountains can't be fully presented if we don't describe their heart - the beautiful Bohinj lake. When someone mentions Slovenia, most of people around the globe will associate it with Bled lake. That one is nice too, I admit. But it's busy, touristically developed, with many hotels around. Bohinj however is still very much unspoiled. Nature is still preserved there, above its northern shore there's mostly still a complete wilderness. If going just on a short sunday hike or bike tour, we always drive thode 20 minutes more, from Bled into the nice Bohinj valley.
Bohinj lake lies towards the end of the big Bohinj valley, on the altitude of 527 m. It is 4.35 km long and maximum 1 km wide, with the depth reaching 45 meters. To encircle it, you will do a hike (or partially bike) of around 11 km.
The origin of lake is tectonic, but heavilly impacted by glaciation. In the last ice age, till some 10.000 years ago, the valley was filled by a glacier, stretching out to Bled and Radovljica. Its maximum thickness some 20.000 years ago was even 800 meters.The rests of morains are still today clearly seen, for examples the hills near Bled. In addition to the waters of Savica river, the lake gets up to 40% of its water also from the underground sources along the northern shore.
Just north of the lake there is Pršivec mountain, 1761 m, and Fužinarska planota (high plateau), so that shore is steep and high. On the southern side the rocks of Vogel and the remaining slopes of South Bohinj Chain are a bit more remote. To the west there is first the Ukanc meadow (Ukanc = 'V koncu' = 'at the end'), then after a few kilometers the Bohinj valley ends with the walls of Komarča. There is the source of the main tributary - Savica waterfall. And towards the east Sava Bohinjka river flows out and the valley winds towards Gorenjska plane.
Bohinj lake is quite cold through most of a year. It's average temperature varies from 1.6° C (February) to only 18.1° C (August), so even in summer the lake is very refreshing and you must be lucky to find it warmer than 20° C. But in winter due to strong currents it rarely freezes completely, and even when it does, skating on the lake can be very dangerous.
From anywhere on the lake shore you have nice views across its surface, but perhaps the best views offer from the eastern shore and western shore. But even more spectacular are the views from above. There are a few lookout points worth mentioning:
An increasing number of people in Bohinj nowadays lives from tourism. They offer there all kinds of organised outdoor activities, on water and on land. For a mountaineering soul the most appealing are: hiking (everywhere), rock climbing (many crags around the lake), mountain biking (valley and slopes above), tour skiing (Komna, S ridge summits and many high mountains on the north), canyoning, paragliding and more and more...
Here are just a few suggestions of possible hikes, starting just from the lake:
In Bohinj valley and above it, you can do several nice bike tours. Here is just one proposal, using the Bohinj Bike Track, and then surrounding the lake (partly on foot). Mountain bike is recommended.
You park on the northern entry to Bohinjska Bistrica, by the bridge over Sava. The bike track (follow the plates), goes all the time by the emerald Sava river. You ride through Brod village, north of Polje village some views on higher mountains open (1). North of Ribčev Laz you best ride to the eastern shore of Bohinj lake (2)(3) and continue to the northern shore (4). There, by half of the lake shore you still have a good road, but officially biking is forbidden there (Triglav National Parc). After you pass the small fishing facility, the road turns into a normal mountain path. Don't worry if on the next 2 km you'll be pushing your bike. Nature is wonderful there. Below Govic you pass a nice meadow (5) with hut, still no road access till there (6). Only when your reach the western shore (Ukanc), you can continue riding your bike again. You cross a nice meadow by the shore and over Savica river gain the main asphalted road. Then you return by the southern shore. From Ribčev Laz it is nice to ride into the Upper Bohinj Valley. So cross the bridge by the nice church of John the Baptist, get on the bike track again and continue towards the NE into Studor village. Nice old houses there. Then cross the main road again and ride to the lower station of ski lift. Continue a bit more, then turn right and climb the nice Senožeta col (7). Nice views from there. Finally descend steeply to Brod village and back to your car.