Sekulinačka planina (mountain), in respect to age and structure, in addition to the surrounding diversity, has a visually esthetical and educational dimension. The forest oases of a virgin-forest type are very few in Papuk, so the interest of nature lovers is to preserve such valuable old forests, and protected them for all times.

Beech-fir forest is about 150 years old in forest area of Gudnoga, and it occupies about 8,01 hectares. The virgin-forest character is preserved in the mature beech-trees with especially qualitative groups of average diameter over 40 cm, and average heights over 32 m, which are interchange with dried and old trees that lie down, or broken from the snow, ice or thunder.

Beech-tree is represented in 85 %, fir-tree in 13 %, and there are individual trees of maple-tree, wolf's-milk, ash-tree, and birch-tree. The resort forest is located on the northeast mountain range, 740 to 820 m above sea level in the highest areas of north Papuk. It is of a very good quality, the concatenation is entire, and the soil is covered with leaves. Everything is left to the naturei.

Special forest reservation is located in the hardly approachable part of Papuk. In order to visit it one has to have a good and expert guide. Sekulinačke planine is protected as a Special forest reservation since 1966.