This 4.5 km ecological nature trail loops around Lake Juodlė and has 12 marked stops. Walking from one to the next, you get to know the landscape, the forests typical of the park, woodland key habitats, bogs, and rare plants, fungi and animals. Along the trail there are information boards and small observation towers. Lake Juodlė was left behind about 10,000 years ago by a meltwater lagoon of the retreating glacier that once spread roughly between Šaukėnai and Užventis. Later its water cut through the Vainagiai–Raudsparnė ridge and drained away through the ancient Venta–Dubysa valley, leaving a plain with small streams and lakelets on the bottom. The climate was arctic then, so a cold desert formed on the eastern shore of the lagoon. Winds blowing from changing directions heaped up dunes, whose hummocks became overgrown with forest as the climate warmed. Over thousands of years the lake in the Juodlė hollow aged, and billions of dead microscopic organisms settled on its bed. Their remains and mineral matter built up a layer of sediment 1.5–5 metres thick, while the decayed remains of larger plants formed a peat layer up to three metres thick, and the lake edges became overgrown with aquatic plants. The lake is fed by a spring-fed stream that never dries up or freezes, and in its southern part several shorter spring rivulets flow in. The lake is fairly rich in fish: in winter you can catch pike under the ice, and in spring and summer tench, roach and rudd bite. In terms of bird diversity, Juodlė is the richest lake in Kurtuvėnai Regional Park: about 30 bird species can be observed here during the nesting and breeding season. In 1967 Lake Juodlė was declared a waterfowl reserve. Juodlė Hill is the last stop of the trail, offering an expressive view of forested hills, the reed-fringed lake and cottages on the shore. You can also relax at Juodlė by swimming and fishing. The trail around Lake Juodlė is about 4.5 km long and takes about 2 hours.