Dozens of people gathered in the Guildhall Square on Saturday to call for the release of Marian Price.
Rally organisers say 57-year-old Ms Price has been held in solitary confinement at Maghaberry Prison for eight months without charge and she should be released immediately. She was arrested after holding a piece of paper for a masked man at an annual Easter Rising commemoration in Derry, a few days later Secretary of State for Northern Ireland Owen Paterson revoked her release from prison on license.
Organiser and community activist Pauline Mellon says the public should be outraged that a woman nearing 60 is being held without proper charge in total isolation.
"I don't support Marian's politics," said Ms Mellon, " I am not a republican or part of any organisation. I organised this rally because I cannot stand back and watch someone her age being treated like that. It is basically internment without trial all over again. We are ordinary people calling for her release. We had Pat Ramsay MLA and Eamon McCann there supporting us on Saturday, which was actually the United Nations Human Rights Day. We wanted people to look beyond politics at this case. She is being held without charge, on her own in a male prison. This is 2011. It is not right."