In this article, we aim to understand how planning theory and practice should approach new urban entities and their transforming meanings. We argue that planning practice has difficulties in identifying and recognising developmental processes where the human attachment to the local environment gradually changes the identity and use of an area. Instead, these processes are interpreted as disruptions in the planned course of action. We illustrate our viewpoint with an empirical example from Finland. The case is about a significant spot of biodiversity in a completely man-made environment. The study serves as an example of how artefacts actively co-shape the events and environment around them and thus create a relationship between humans and their surroundings. Drawing on a science and technology studies-inspired perspective on the relationships between human and non-human actors, we stress the importance of artefacts, local setting and processual development in urban planning.