Seems like this used to be a biggie:
“Stone circles vary very much in size ... one at Innesmill, Urquhart, is 120 feet” – banffshirefieldclub.org.uk/PDFs/BOOK_8/Banffshire_Field_Club_Transactions_1908-1909_-_1909_The_Stone_and_Bronze_Ages_in_Scotland_WM.pdf
“Perhaps the largest is one in the parish of Urquhart, which is a hundred and twenty feet in diameter.” – banffshirefieldclub.org.uk/PDFs/BOOK_9/Banffshire_Field_Club_Transactions_1910-1914_-_1911_Sepulchral_Stone_Circles_WM.pdf