The unfinished frame is not completed and not romanticised. It becomes the support for a reversible steel ecosystem where sport, vegetation and public life can keep changing position. Concept Terzo Tempo turns an unfinished concrete structure at Scalo San Cristoforo into civic infrastructure for sport and collective life. The abandoned frame and its spontaneous landscape are kept as an open matrix rather than completed or restored. Compressed between railway, Naviglio Grande and viaduct, the site is treated as a fragment of landscape rather than an empty plot. The ecology that has occupied the ruin becomes part of the project, setting the terms for new public ground. System A reversible steel structure inserts suspended rooms for training and flexible sports halls into the existing grid. At ground level, paths connect exhibitions, pools, climbing areas, gardens and the Naviglio, reopening the former enclosure as an urban park. credits Project team: Cristian Casiraghi, Federico Martorana, Anita Rizzi, Chiara Tabladini. Professors: Filippo Orsini, Estefania Cuenca Asensio. Tutors: Michele Deconti, Carlotta Oliosi, Michelangelo Sicari. Politecnico di Milano, Architectural Design Studio, A.A. 2025/2026.