This JRC collection anchors the language of transformation in the uneven, material histories of contaminated European sites. Its case structure spans national regulatory circumstances, actual remediation technologies, legacy industries and redevelopment programmes, including examples from Belgium, Finland, France, Hungary, Italy, Poland, Spain and the United Kingdom. The report makes contamination legible as a variable that changes the available future rather than as a decorative symbol of urban abandonment. Technical feasibility, public investment, risk to health, regulatory capacities and subsequent land use do not align automatically. The juxtaposition of national experiences reveals a second complication: a European method may share a vocabulary while its permissions, remediation thresholds, liability and costs remain jurisdictionally situated. The document bridges geoscience, engineering, environmental health, landscape reconstruction and public administration; its strongest operation is material constraint. A spatial proposal that has not established what can be touched, occupied, removed or left undisturbed cannot yet claim to be reversible, participatory or publicly beneficial. For The Waiting City it demands an explicit difference between a research inventory and a site capable of implementation. For HoodKnows it is a useful counterweight to treating environmental quality as a perceptual matter alone: lived experience can challenge an indicator, but it cannot annul documented toxic exposure or specialist safety thresholds.