The Thomsen Round Barn was an historical structure located near Armstrong, Iowa in rural Emmet County, Iowa. It was built in 1912 and was listed on the National Register of Historic Places since 1986. The building is a true round barn that measures 65 feet (20 m) around. The first floor is constructed of concrete and the second floor consists of white vertical siding. It features a two-pitch conical roof, and a 16 feet (5 m) central silo. The barn is no longer standing.