The trip, conducted under tight security and closed to the press who will be taken there on Monday, was difficult but cathartic, Health Minister Anne-Grete Strøm-Erichsen said, according to Norwegian news agency NTB.
"For some it was very difficult but I think that the majority found the answers by coming here: it was important for them to come," she said.
Police inspector John Stamnes added: "Some wanted to know as much as possible, the others were more reticent. But all of them wanted to see the place where a family member was killed or wounded."
The self-confessed perpetrator, Anders Behring Breivik, is being held in solitary confinement.
In a manifesto he published on the Internet just before the attacks, Behring Breivik professed his hatred for Western-style democracy, saying it had spawned the multicultural society he loathed.
At the time of the attack, the ruling Labour Party's youth wing was hosting a summer camp on the picture postcard island near Oslo.