Kawainui Marsh was once the basin at the center of the Koolau volcano caldera; the great crater encircled the Windward side of Oahu and stretched out to the bay.
It is now a wildlife refuge and home to four species of endangered water birds: the Hawaiian stilt (aeo), the Hawaiian coot (alae keokeo), the Hawaiian gallinule (alaeula), and the Hawaiian duck (koloa maoli).
The open marsh provides little shade so it is best to go early in the morning or late in the afternoon.
The paved path is great for strollers.