With impassioned appeals for love, hope, and unity as Colombia enters the post-conflict phase, President Juan Manuel Santos and 25 other Nobel Peace laureates kicked off the 16th World Summit of Nobel Peace Laureates, a three-day conference touted as one of the world’s most important peacebuilding gatherings.

In front of a packed auditorium at the Corferias Exhibition Grounds, Santos welcomed the Nobel Peace laureate as the event’s organizers declared Bogotá, which is the first Latin American city to hold the event, the “city of peace,” an honor bestowed on the summit’s host city each year.

“We are honored and happy to have such a select group of men and women here…” Santos said. “Your brilliance, your experience…will be welcome in this challenging post-conflict phase that we are just barely starting. That is why it is so important to have you here with us, and that is why we want to…learn from you.”

The summit comes as Colombia marks what it hopes is the beginning of the end of a 52-year war that killed 220,000 people and displaced 7 million. As Santos spoke about the challenges of implementing the peace accord with the Revolutionary Armed Forces of Colombia (FARC), thousands of FARC rebels continued pouring into 26 demobilization camps around the country, where they will turn over their weapons, reintegrate into society, and form a pacific political movement. And in Chocó, the National Liberation Army (ELN) released former congressman Odin Sanchez, which is expected to clear the way for formal peace talks with Colombia’s second-largest rebel group next week in Quito.

The opening-day fanfare started with a rousing tribute to Colombia’s indigenous communities and conflict victims in which people dressed in white danced while tossing white shrouds that were fastened to a circular platform in the middle of the auditorium about the crowd as drummers pounded on tambores.

Afterwards, three Nobel Peace laureates spoke about peacebuilding. José Ramos-Horta, a former president of East Timor and winner the Nobel Peace Prize in 1996 for his efforts to find a diplomatic solution to armed conflict in the Southeast Asian nation, praised Colombia’s peace process and the country’s transformation since his visit in the 1980s to negotiate the release of hostages held by the ELN. Tawakkol Karman, a Yemeni journalist and activist who won the Nobel Peace Prize in 2011 for her efforts to promote women’s rights and participation in peacebuilding, referred to victims of Colombia’s armed conflict as “exceptional heroes.”

And Oscar Arias, a former president of Costa Rica and Nobel Peace laureate in 1987 for his role in brokering peace in Central America, told the packed auditorium that Colombia “has become a shining light for the world” and then took aim at the Trump administration, comparing the real estate magnate’s government to George Orwell’s novel “1984.”

The United States is “a country where insensitivity, xenophobia, and hate have grown in a frightening way… the book ‘1984’ by George Orwell is not a faraway threat, but the daily script of leaders,” Arias said.

However, boos quickly filled the auditorium when Bogota mayor Enrique Peñalosa took the podium, especially when he boasted of Transmilenio’s “successes.”

“Hosting this summit is an honor for Bogotá,” Peñalosa said. “We are living through exciting and transcendental times in this country.”

But it was Santos who stole show, receiving a standing ovation.

“Now Colombia faces a new tomorrow…a more promising future without the burden of the armed conflict. But we also know that the signing of the agreement was only the beginning,” Santos said. “The implementation of the agreement…will be as or more difficult than the negotiations.

“You may say I’m a dreamer, but I’m not the only one,” Santos added, quoting John Lennon’s 1971 song “Imagine.”

The opening ceremony was followed by several panel discussions featuring Nobel Peace laureates, cultural events, and music, all of which will continue through Sunday.

The summit was created by the Gorbachev Foundation in 1999, a Moscow-based non-profit founded by former Soviet premier and Nobel Peace laureate Mikhail Gorbachev, who was scheduled to attend the summit but backed out due to unspecified health problems. The event has been held in Rome, Paris, Berlin, Hiroshima, and other European and U.S. cities.