Established in 1991, Koli's 30 square-kilometre national park has a unique geology that spans over three billion years, as well as a diverse animal and plant life. The national park also has an excellent trails network for trekking and excursions.


The summits of Koli's forested hills dominate the surrounding sceneries. The parallel hills, separated by a valley, create a scenic completeness that is both rare and valuable. Taller than its surroundings by 200-250 meters, Koli's rising hills are made up of granite gneiss bedrock that is over three billion years old. Koli is located between two differently aged bedrocks, the south-western one of which is noticeably younger at two and a half billion years old, and composed of Proterozoic bedrock.


Koli's forests belong to the family of northern coniferous trees, known as the taiga. However, the summits and ridges of the hills are largely dominated by boreal forests. Coated in ice and snow, the conifers become an impressive ice sculpture show during the winter. The area also has many fresh boreal forests and groves. Koli has a rich cliff-side vegetation, as well as fens and thriving marshes that are protected by the national grove and marsh protection act. There is an abundant presence of endangered groves and grove vegetation. The birch woods, meadows and natural pastures are well-represented biotypes in Koli. The birch woods are typically bright and immaculate, but can also become grey and unkempt.


The biking routes at Koli's natural park are renowned. Ukko-Koli's stunning scenery is best appreciated from the vantage point of the forest trails. During the summer, Koli organizes hiking trips, including the popular Herajärvi tour. Pielinen, a pristine and prominent lake, is as unique an experience during summer as it is during the winter. During the summer, the cruise, along with rowing and swimming, create the basis for a successful vacation. As an ice desert during the winter, Koli is an exotic destination for even the most experienced nature hikers. The snowy forests, hills, and the snow shoe trails provide the visitor with a memorable experience in an enchanting environment. For visitors with reduced mobility, Koli offers great opportunities to admire the landscapes from vantage points that blend in with nature.


When visiting the national park, there are bylaws that ensure that nature is respected. This is remarkably achieved in Koli. In 2007, Koli's national park was granted the European Charter for Sustainable Tourism in Protected Areas certificate.