Families tested their kites against blustery winds, some hiked the more than 300m to the top of the cone, while others listened to speakers talk about the flora and fauna and the history of the Hereweka/ Harbour Cone land.
The council officially took possession from the Maori incorporation proprietors of Akapatiki A Block on July 1. It bought the land in January for $2.6 million.
About 400 people took a free shuttle bus from the Portobello domain to a section of the 328ha property on Highcliff Rd.
Cr Dave Cull said the open day was a chance for the public to see the asset the council had acquired for future generations.
The land would remain as a working farm for the "foreseeable future", with plans for walking tracks, car parks and information panels in the next few years.
Unique sections of bush would likely be fenced off to protect them from the public, he said.
There was also the possibility of promoting traditional farming activities as a visitor attraction.
