These are speculative interventions in public space/potential collective spaces in the city of Basel, Switzerland. This is one of the 6 proposed projects and is a hidden garden: it turns Basel's underground river, Birsig, into a botanical garden, hidden underground, but open for public. Lights, hydropon­ic technology and heaters transform the tunnel’s contained microclimate into warm and humid space.

- Grace

https://www.archdaily.com/877007/kosmos-architects-explore-6-speculative-public-projects-for-city-of-basel