Organised by the Dunedin Secondary Students Climate Forum, made up of 3000 pupils, and endorsed by the Dunedin City Council, the group set up stalls around town, staged activities and approached businesses to get on board by charging for plastic bags.
Proceeds are going to the Orokonui Ecosanctuary.
Organiser Paul Young said reusable bags, donated by Progressive Enterprises, were exchanged for shoppers' plastic bags.
At the end of the day, these plastic bags were chained together and strung through the Octagon for an "amazing" public display.
The group believed plastic bags were not free because of the environmental, economical and social costs involved in their creation and disposal.
Mr Young said the notion focused on the community and was "something everyone can identify with".
He hoped the initiative would "change people's mindset".
