As cities evolve, urban infrastructures need to be updated, and if they fail, they will become abandoned and facilitate the creation of an urban phenomenon called “brownfields”. Since the past decade, abandoned or derelict sites have been spread out throughout developed urban areas worldwide. Brownfields may cause several problems for urban development, the economy, social values, and the environment. If they are left, more greenfields will be exploited, and urban sprawl will develop. The challenge is to be addressed in different ways in cities, though. Today, one of the urban development plans in major cities such as Copenhagen is to regenerate brownfields to benefit from these potential opportunities for improving social, economic, and environmental values.