May [2017] Puzzle: where’s this….?

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….of which Thomas Hardy wrote in 1881:

“To the south, in the direction of the young shepherd’s idle gaze, there rose one conspicuous object above the uniform moonlit plateau, and only one. It was a Druidical trilithon, consisting of three oblong stones in the form of a doorway, two on end, and one across as a lintel. Each stone had been worn, scratched, washed, nibbled, split, and otherwise attacked by ten thousand different weathers; but now the blocks looked shapely and little the worse for wear, so beautifully were they silvered over by the light of the moon.”