Pope Francis prayed for healing from what he called the "terrible effects of colonisation" as he led a pilgrimage to Lac Sainte Anne on Tuesday in Canada.
It was the last public appearance in Alberta before heading to Quebec.
The Canadian lake has been known to indigenous peoples for centuries as a sacred place of healing.
Every year on the Catholic feast day of Saint Anne, the grandmother of Jesus, tens of thousands of Cree, Metis, Blackfoot, Dogrib and First Nations Indigenous people make the pilgrimage to dip in the lake.
At one the Pope used a traditional wooden tool with a brush on the end to bless the crowds of people.
The pontiff's six-day visit to Canada is to atone for the Catholic Church's role in running residential schools that forcibly assimilated the country's indigenous children into Christian society.
Earlier, Francis presided over Mass for tens of thousands of Canadians at a stadium in Edmonton.
The 85-year-old traded his wheelchair for the 'Popemobile' to greet the enthusiastic crowd.
The joyful atmosphere follows the solemn events on Monday when Francis travelled to Maskwacis to beg forgiveness from Indigenous survivors of the residential schools in Canada calling their treatment a "deplorable evil."