This project is an experiment in exploring ways for various species to coexist within cities, moving away from a human-centric perspective of nature. We propose a method to fully return one of the symbols of the 20th-century Industrial Revolution, the urban "elevated highway," back to nature. The 'Inner Ring Road' in Seoul, South Korea, which passes through nearly all mountains and rivers in the northern part of Seoul, implies the potential for a natural infrastructure that could connect all these mountains and rivers. We present prototypes tailored to the diverse contexts of urban elevated highways, transforming these highways into eco-ducts that serve as natural arteries for Seoul, spreading outwards and evoking the image of a 21st-century 'Noah's Ark' as the project name suggests.