Hochstetter Pond is a volcanic depression in an Auckland Council reserve on Grotto Street in Ōnehunga, surrounded by houses. The hollow is about 60 metres wide, with steep sides of volcanic rock. It was possibly formed when a lava cave collapsed, and it is considered part of the One Tree Hill lava flows. At its base is a Machaerina sedgeland wetland, an ecosystem that is critically endangered, and many native fauna species live there.
The wetland is deeper in the northern part and is flooded in winter and after heavy rain. The area is recognised in the Auckland Unitary Plan as a Significant Ecological Area and an Outstanding Natural Feature. Volunteers and Auckland Council are restoring the site, with weed control and native planting on the steep slopes. Few natural wetlands of this kind remain on lava flows in urban Auckland, which gives the pond its importance for the city's biodiversity.