Single huge standing stone pillars are called monoliths or megaliths. There are a great many of them in UK and France. Search "Archaeology Megaliths" brings up dozens of sites. But I did not find one worth citing here.
P.S. Somebody mentioned the word "dolmen" which I had been unable to remember. Searching for "archaeolgy dolmen" brings up a lot of sites. Somewhere I saw pictures of France with long rows of them. No clue as to motivation of the people who erected them.