By Elliott Gotkine
BBC correspondent in Buenos Aires
Argentina's naval school, which operated as a torture centre during military rule, has been handed over to the government to become a museum.
Nestor [standing, left] asked the crowd to forgive the state
Thousands witnessed President Nestor Kirchner sign the agreement, at a ceremony marking the 28th anniversary of Argentina's last military coup.
The ceremony was held in the grounds of the school itself.
Human rights groups estimate up to 35,000 people died or disappeared in the 1976-1983 dictatorship.
In the Navy School of Mechanics, it is thought that up to 5,000 people were tortured or murdered.
Symbol of terror
At the ceremony, some carried placards bearing the names and photos of their lost loved ones.
Others wore badges identifying themselves as survivors of Argentina's clandestine torture centres, which terrorised thousands of civilians during the country's last military dictatorship.
The worst of these centres and the most potent symbol of what became known as Argentina's Dirty War was the Navy Mechanics' School.
Of around 5,000 people detained here, many were tortured, drugged and then thrown out of aircraft over the Atlantic Ocean, never to be seen again.
Other victims gave birth inside the building, only for their babies to be snatched and handed over to military officials to be raised as their own.
Many of those who were tortured and survived the Navy Mechanics' School attended the ceremony, cheering when Mr Kirchner signed the agreement.
Just over half an hour later, the president addressed the crowd and asked for forgiveness on behalf of the state for having kept quiet, during the past few decades of democracy, about the atrocities committed in Argentina.