The volume of the oak trunk is 4.98 m, diameter about 1.6 m, height about 26 m. According to rough estimates, Grybiškės oak is about 1000 years old. Grybiškės oak grows in Nemkamedžio forest, about 2 km southeast of Poškoniai village. Road signs lead from the regional park’s visitor center to the oak. The largest Lithuanian boletus was found near Grybiškės oak, which is registered in the Lithuanian record book. The boletus weighed 3.05 kg and the diameter of the cap was 49 cm. Jonas Kuklys, a resident of Grybiškės village, found the boletus in 1971.