Christmas type holiday that can be thrown into any city/town.
The addition of “irrelevant” details adds local colour to a campaign world, giving the impression that the DM has thought very deeply about the history of even the smallest architectural feature.
A little way up the narrow valley, before they reach the woods, the PCs notice the squat, tumbledown buildings by the riverside. They are hardly big enough for a human to stand in, and the complex cogs and shafts that occupy the central cavity of one of the buildings are perplexing. What were these buildings? And how safe are they to explore?
Alternatively a desolate place is the perfect setting for a derelict chapel or croft. There needn't be any actual physical encounter involved, but it adds atmosphere to a place to see its dead history. For instance, in the Outer Hebrides there are whole deserted villages which were razed to the ground by the English during the Clearances. Such stories give a setting authenticity and character.