In the village of Danki just outside of Serpukhov is the Prioksko-Terrasny Biosphere Nature Reserve which occupies almost 5,000 hectares on the left-side of the River Oka. It was established in 1945 and in 1979 was included in UNESCO's Man and the Biosphere Programme. The reserve is especially famous for its herd of European bison known as zubr which can be visited as part of an excursion. Tickets can be bought at the excursion centre at the entrance to the park in Danki.