Doorway into the sky

Walking back from the beach today I stopped to look at where these steps led to. There are several sets leading up the cliff, possibly once connecting clifftop gardens to the beach path, some in quite a poor condition but this looked more stable. The cliff is always changing, bits falling off and properties ending up perilously close to the edge. All very reasonable you might think but what is this strangeness?! I could hardly believe my eyes to see an apparently unconnected doorway behind the fence on the edge of the cliff. The mind boggles - is it a doorway to the sky? An actual stairway to heaven? A builders dunny with the door left open? 
What do you think blippers?