Heritage Open Day: Run by English Heritage volunteers, the northern henge tour explains how ordinary Neolithic people built this extraordinary complex. The northern henge is the best preserved, demonstrating the amazing construction abilities of our Neolithic ancestors The Neolithic people were extraordinary monument builders and this unique triple henge complex is an incredible example of their work. Thanks to later tree planting, the Northern Henge is the best preserved of the three. with banks over 3m high and ditches approx. 3.5m deep, near to how they would have looked when they were originally constructed. Unlike the central and southern henge which were more recently used for agricultural purposes, the northern henge was planted as managed woodland.