"vast circle" is a correct and usable phrase in written English.
You can use it to refer to a very large group of things, people, or ideas. For example, you could say, "This issue has caught the attention of a vast circle of concerned citizens."
Blessed with a vast circle of devoted friends, Marita loved life, was passionate about politics, literature and gardening.
She will be missed not only by her immediate family, but also her extended family and vast circle of friends.
A legendary figure in 20th-century number theory was Paul Erdős (1913 96), a Hungarian genius known for his deep insights, his vast circle of collaborators, and his personal eccentricities.
In a solo from Jessica Lang's "Splendid Isolation II," Tyler Brown commanded attention as an Ailey queen should, her outsized white skirt spilling in a vast circle around her.
In New York, the loss has simply left a mournful hole in the vast circle of friends that Mr. Parrado had collected during his seven years in the city.
His vast circle of friends gave him an instant constituency to bear witness to his good deeds; the extraordinary nature of his death -- he is listed by the medical examiner's office as victim No. 1 -- gave him fame.
Yet at the same time, the fact that so many members of this once-vast circle have faded back to the rhythms of their daily lives, and that there is no longer someone there every hour of the day, suggests the extent to which New York is moving, slowly, though certainly, beyond the horror that consumed it.
IT LOOKS like a planetary tattoo designed to be seen from space, a vast set of concentric circles inscribed in the skin of southern California's desert.
He concluded that "ideas of England" depend on "a system of vast circumferences circling round the minute neighbouring points of home".
The village of Avebury in Wiltshire is surrounded by a vast stone circle as well as a huge circular earthwork.
When she referred to the audience as "we" and "you," she was conjuring up not a coterie of the like-minded but a vast, contentious circle of friends and lovers, a utopian community that transcended time and geography.
