It occupies the steep eastern slopes of the valley of Waskerley Beck, alongside and downstream of Tunstall Reservoir, some 3 km north of Wolsingham and is one of the largest expanses of semi-natural woodland in west Durham.

[1] The area once formed part of a much larger expanse, Wolsingham Park, which was owned by the prince bishops of Durham from the late 13th century, and was protected both for its deer and for its timber.

In wetter areas, alder, Alnus glutinosa, is dominant, over a ground cover that includes soft rush, Juncus effusus, meadowsweet, Filipendula ulmaria, and tufted hair-grass, Deschampsia cespitosa.

[1] On base-rich soils, the woodland typically consists of ash, Fraxinus excelsior, and wych elm, Ulmus glabra, over an understorey of hazel, Corylus avellana, and bird cherry, Prunus padus, and a rich ground flora that includes lady-fern, Athyrium filix-femina, male fern, Dryopteris filix-mas, and hard shield-fern, Polystichum aculeatum.

One, which is favoured by Durham Wildlife Trust,[2] relates the name to the ancient lead-smelting industry, in which a "baal" (or "bail") is said to have been a local term for a pit in which lead ore was "boiled" to remove impurities.