Seoul is located in a valley surrounded by mountains with one mountain in the center, Namsan. On top of Namsan is Namsan Tower which is considered an iconic image of the city of Seoul and can be seen from almost anywhere in the city. To maintain this line of sight, many developers have had to set height limits on their buildings. The city also has strict laws about building heights for reasons of national security stressed by the Korean Air Force and U.S. Air Force.