Some 2 million people are also expected to flock to the city in late July for WorldYouthDay, a Roman Catholic pilgrimage that Pope Francis is scheduled to attend.
This is Pope Benedict's second visit to Spain since his election, and a third visit is planned next year for WorldYouthDay, a sign of how important the Vatican considers the health of the Church in the country.
The conference will be followed by a one-day World Heritage Youth Summit on 1 October, sponsored by Historic Scotland, which will bring together 45 young people to explore what World Heritage means to young people in Scotland.