Kaluzhskiye Zaseki Nature Reserve, Nature reserve in Ulyanovsky District, Russia

Kaluzhskiye Zaseki Nature Reserve protects roughly 185 square kilometers of land with old-growth forests containing broadleaf trees, pines, and northern species across different soil types. The reserve is divided into sections that provide various walking routes and woodland environments.

The reserve was created by a Russian government decree on 5 November 1992, covering 18,533 hectares in two tracts 12 km apart. Its name comes from the Zakotskaya abatis line of the 16th and 17th centuries, when felled trees formed a defensive barrier against southern raids. From the 18th century the name referred to part of Kaluga Governorate, including the Kozelsk and Peremyshl abatises. In 1712 the Tula arms factory and the Bryansk admiralty became the main consumers of timber from these forests, which were managed by the Artillery Office.

The reserve's name comes from medieval defensive timber barriers that once protected the Kaluga region from invasions. Today, visitors can learn about the local forests and conservation methods at an education center located within the protected area.

The northern section has roughly 2.7 kilometers of marked trails with information boards, while the southern area offers about 5 kilometers of circular walking routes. Wear sturdy footwear and be prepared for wet conditions in the forest, especially in damper sections.

The reserve works with Orlovskoye Polesye National Park to reintroduce the European bison to Central Russia; by 2013 the herd numbered 84 animals and was judged healthy and growing. The bison favour forested tracts with small meadows. The reserve is mostly closed to the public, so sightings are not guaranteed and visits need permits arranged in advance.