Game & Nature Reserves Game & Nature Reserves The Bolmke is a stadtnahes nature reserve in Dortmund south of the Signal Iduna Park (formerly Westfalenstadion) and the Westfalenhallen with a size of 52.1 ha. The nature reserve Hallerey lies about 5km northwest from Dortmund city center and has a size of 72.1 ha. The reserve is provided for the first time on 12 September 1977 in the protection. The Nature Reserve Dellwiger Bach is located in Dortmund Municipality Lütgendortmund in North Rhine-Westphalia , Germany. It covers 112.1 hectares.