Parallel Universe

After yesterday's gemstones and parallel lines I unwittingly came across this curiosity on my walk today along the old disused railway line leading to Princetown on Dartmoor. Strangely, I must have walked past it many times before but never noticed it. 
To avoid any suggestion that I might have  become trapped in a parallel universe I have also included a couple of extras from my walk. The first is a hawthorn tree near to this fence and the second is the ruin of a stone building at Swelltor quarry which the old railway line snakes around.