Though not true barns, the following two buildings share many design cues from round barns, and of course, a round shape!!
The Stepan Center Gym is located on the campus of Notre Dame University. I remember going here for some choral performances I was singing in for the Bicentennial Year, 1976. I remember being impressed by the geodesic dome, a la Buckminster Fuller.

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Another round barn shaped building is the St. Joseph County Jail:

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