From WCC website

Rain Gardens: Explained

The Swan Lane and Garrett Street upgrade is not only bringing a fresh look and feel to Cuba Street, but introducing the first pair of built-in rain gardens to Pōneke – a natural way of removing pollution from storm water run-off before it enters our streams and reaches our harbour. 

As the official pilot for rain gardens in the capital, these gardens are not only special because they’re the first-of-their-kind, but also because of the cultural significance of the Waimapihi Stream that they flow into.

Read more about the gardens on Our Wellington.