Climate change and biodiversity losses are considered to be two of the main crises of our current time. But how sustainable is our detention system? On a micro level, how could greenspace in detention houses be supportive in solving these issues? On a meso-level, what should be taken into account when looking at the architecture and energy supply of detention houses? And what about (social) sustainability as a topic of long term visions? What changes should be made in policy in order to create a positive impact on both our society and our environment?