Opapaka Pa was a small defensive pa built and used by Ngati Hia in the late eighteenth century. The Ngati Hia people lived in the valley to the south and would withdraw to the safety of the pa in times of trouble.
From the site there are fantastic views over the area, including other Maori fortifications, the mountain ranges of Rangitoto, and more distant Ruapehu.
Informative panels along the track to the pa tell you about traditional uses of many of the plants seen along the way. On the highest part of the ridge is the pa site where a panel outlines its history.