Public spaces reflect the social life and interaction of people When this social interaction is missed in a public space it means the public space is lost. Lost space is a production of urban space left by people if it continues, we will lose the place. In the lost space we just have an unusable land in the urban environment whereas, when we lost a place not only people’s memories and imagined being forgotten from a space but also the identity to be lost and the characteristic of the city and citizenship will decline sharply. The perceptions of the environment due to differences in humans and some special factors in their way of life are not the same so the meaning of lost space between residents and passersby is different. The variables of space, which associate the meaning of lost space for people, were not identified;so there is a big gap in designing lost spaces to bringing back to the people and life cycle. This study has concentrated on the lost space to identify the variables of it which convey the meaning of lost space to people, also comparing the perception of residents and passersby of a lost space in the urban environment to extract the perceptual factors of lost space.