My favourite ancient example are the vitrified forts found in Scotland and a few other places - large amounts of stone walls partially melted - nobody knows how this was done or indeed whether it was intentional:
One of the larger vitrified forts, Tap O' Noth, provided me with imagery that I used to visualise Weathertop from LotR - this was well before the movies.
I did even check to see if Tolkien had ever visited the area to see if there was any connection but no luck - unlike, for example, Lauterbrunnen in Switzerland being the real world Rivendell.
You've got it the wrong way round - the last King of Scotland actually also became the King of England, the countries were united by a political process some years later - largely to pay off debts following one of the most ill conceived colonisation attempts in history:
https://en.wikipedia.org/wiki/Vitrified_fort