Hold It: Folke Köbberling & Martin Kaltwasser: The Art & Architecture of Public Spaces

Collaborators since 1998, German artists Folke Köbberling and Martin Kaltwasser (also an architect) have created "amorphous forms out of trash that retain a childlike simplicity in spite of rigorous engineering," according to the UK's The Guardian. Their "magical, structurally sound and user-friendly" sculptural works make use of repurposed materials, volunteer labor and offbeat public spaces.