Rivonia Trial
Following Mandela's five year prison sentence, in July 1961, the government launched a raid on an ANC hideout in Rivonia, South Africa. During the raid they were able to gather enough evidence to charge and convict Nelson Mandela along with seven others on accounts of sabotage, treason, and violent conspiracy against the government and they were sentenced to life imprisonment (nearly escaping the death penalty.) This trial received a lot of international recognition and acted as a prime example of a martyr suffering under oppression of strict and unjust system of racial segregation.
Robben Island
Mandela was incarcerated at Robben Island prison, located miles and miles off the coast of Cape of Good Hope, from 1964 to 1982 until he was transferred on two separate occasions up until his release in 1990. The conditions at Robben Island were very poor and the inmates were issued small cells without bedding, and because Mandela was a political prisoner he received much smaller rations. Although it was a struggle Mandela was able to earn a degree in law while imprisoned and act as an advocate for many of the other prisoners. Mandela was also offered on multiple occasions, for his freedom in return for non-violence and retirement from his active role in politics from which he repeatedly refused. It wasn't until February 11, 1990 when he officially "freed" by former president F.W. De Klerk.