The badly eroded remains of a World War 2 pillbox on the beach at Challaborough, near Bigbury-on-Sea, Devon, England.
Some stone steps can also be seen in the cliff above the pillbox.
https://archaeologydataservice.ac.uk/archives/view/dob/ai_full_r.cfm?refno=6597
888 photos taken in August 2021 with a Sony a6000 and processed in Reality Capture.