Architecture and urban design are public art forms that people experience through their daily activities in cities. While other art forms can be avoided, people cannot choose to avoid experiencing the built environment as they move through urban spaces. Aesthetic preferences in environments are influenced by both natural and learned social and cultural factors, and Jack Nasar identified five attributes of liked environments: naturalness, upkeep, openness, historical significance/content, and order. As people experience cities through movement, Gordon Cullen's concept of "serial vision" describes how urban design can create a series of revelations and contrasts that engage observers as their viewpoint changes.