Hundreds of people go back to Utoya camp, Norway while some 1,000 enroll in its activities four years after far right Anders Breivik killed 69 people on the island on July 22, 2011.
The Labor Party's youth wing who owns the island organised the gathering after the July incident shocked and affected almost the whole country.
A memorial was made on the island for the teenagers lost that day.
Breivik disguised in a police uniform killed the guard of the camp and the people attending. He is currently serving a 21-year prison sentence.
Sverre Outhouse who survived the attack said that he has "been through a lot" but he had to attend the camp again and have a "great time."
Police chief Kjell Magne Tvenge said that police are protecting the island during the reopening this year to make sure safety is maintained.