She said her government will move to repeal an amnesty law that has prevented prosecution of human rights violations.
Ms Bachelet and her mother, Angela Jeria, were held on the Villa Grimaldi farm for several weeks in 1975. They went into exile after their release.
Ms Bachelet said the Inter-American Human Rights Court recently ruled that the 1978 amnesty law issued by the regime of ex-dictator General Augusto Pinochet violates the international law that bans the amnesty of crimes against mankind.
“The government will soon announce measures that will ensure that the Chilean state will act in accordance to international law,” she said. “There is no place more appropriate than this one to announce this.”
Since the end of the Pinochet regime in 1990, the right-wing opposition in congress has blocked efforts to repeal the amnesty law.
Pinochet, 90, is under indictment on torture and kidnapping charges for the abuses at Villa Grimaldi.
The one-time detention centre has been turned into a memorial for the 4,500 people who were held there between 1973 and 1978. Most were tortured, many killed and more than 200 never heard from again.
According to a report by a commission appointed by the first post-Pinochet civilian government, 3,197 people were killed for political reasons under the 1973-1990 dictatorship.
Ms Bachelet appeared tense as she arrived at the former prison, but looked relaxed as she toured the area. She also visited the Tower, a tall wooden structure where the worst tortures occurred, according to victims’ testimonies.
“That was a place of death,” she said. “Terror did not prevail. Life and peace have been stronger.”