Puszcza Zielona (Polish: [ˈpuʂt͡ʂa ʑɛˈlɔna]; lit. 'Green Wilderness') is a forest in Poland which extends from the Narew River and the border of what was once East Prussia. It is bounded on the east by the Pisa River and on the west by the Orzyc River. The forest lies in a lowland and contains a wet sandy soil, but it is rich in various minerals which are mined.