Eskrigg Wood appears to be the site of a crashed rocket. The tail fins and a short section of body are all that remain. Watch for nettles and brambles. The wood is CROW access land so you can wander freely.
At the N end of the wood is a strange stone arch, which reminds one of a lime kiln, but I don't think it is as there's no 'kiln' above it. It also looks unstable!