This section of the Hertfordshire Grim's Ditch crosses the Ridgeway National Trail in woodland at Aldbury Nowers on the Chiltern escarpment. Described as a prehistoric boundary monument, the age and purpose of the ditch is the subject of debate.
<a href="//commons.wikimedia.org/wiki/User:Alansplodge" title="User:Alansplodge">Alansplodge</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>