The Seven Lakes Valley (Dolina sedmerih jezer) is a chain of glacial tarns strung along a high karst valley between 1,300 and 1,990 metres, north-west of Lake Bohinj inside the heart of Triglav National Park. It is one of the most famous walks in Slovenia and a classic two-day trek with an overnight at the Triglav Lakes Hut.
The standard route starts from the Savica waterfall trailhead and climbs steeply for four hours to the Black Lake (Crno jezero), the lowest of the seven and the only one you can reach on a day hike. Strong walkers can carry on the same day to the Triglav Lakes Hut at 1,685 metres, eat dinner, sleep, and continue the next morning past the Double Lake and the Green Lake to the highest tarn at nearly 2,000 metres. Book the hut in advance — it is full all summer.