Tlstá is a mountain in the Bralná Fatra part of the Greater Fatra Range, measuring 1,373.3 m (4,506 ft). It is located over the Turiec Valley, rising steeply nearly 1,000 m (3,300 ft) above the valley bottom. It has rugged slopes with many rock spires and rock terraces under the grass-covered summit. With its well-preserved forests, rare plants and many karst caves in the massif, the mountain and its surrounding area were declared a National Nature Reserve in 1981, covering an area of 30.66 km2 (11.84 sq mi). Together with the opposite Ostrá Mountain and Gader Valley beneath them, they create one of the most valuable and picturesque parts of the Greater Fatra Range.