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Two thousand young people from 190 countries have arrived in Belfast for the One Young World summit.
The four day event, held in the city’s SSE Arena, will allow delegates to meet political, business, and humanitarian leaders.
Former Irish president Mary Robinson, musician Sir Bob Geldof and footballer Rio Ferdinand are among those due to speak.
Northern Ireland delegate and climate change activist Emer Rafferty, from County Armagh, told BBC News NI collaboration and networking were at the heart of the summit.