The C-2 visa is a non-immigrant visa which allows individuals to travel to United States for the purpose of immediate and continuous transit to or from the headquarters of the United Nations, or for United Nations officials transiting the US to another foreign nation.
The travel area for recipients of a C-2 visa is limited to a 25-mile radius of Columbus Circle in New York City. The visa is valid for the duration of the individual's stay at the United Nations.
References
C-2 visa Wikipedia(Text) CC BY-SA