Located near La Feria Verde in Aranjuez, Parque O2 transforms a neglected railway underpass into a vibrant public landscape. A bold graphic intervention wraps the tunnel in color, turning infrastructure into a neighborhood landmark. The project incorporates air-purifying paint that helps capture emissions, reinforcing its environmental intent. Along the hillside, gradient bamboo poles integrate reflective bands, creating a subtle night presence and extending the experience beyond daylight. Through color, reuse, and ecological strategies, Parque O2 reclaims residual space as a playful, sustainable place for community and wonder.