The Iron Age Hillfort At the back of Fish Pond is the Iron Age Hillfort, Mynydd Y Castell. The slopes are covered in mature beech and sweet chestnut trees. These trees provide chestnuts and beech mast that the deer feast on during the autumn. This food gives their diet an extra boost before winter sets in. The autumn colours over the hillfort are spectacular especially following a very dry summer. Several fallen trees have been left to provide habitat for insects. Many species of fungi grow on the wood, this helps it to rot and returns nutrients back into the soil. Some of the mature beech trees show impressive bracket fungi.