The stunt, which is being broadcast live on the internet by video artist Franziska Vu, is a tribute to the estimated 200,000 political prisoners who helped bring down the Berlin Wall 20 years ago.
Holzapfel entered the cell just after midday on Thursday and will stay for one week, living as he did when he served 13 months in solitary confinement in the prison in the mid-1960s.
With plenty of time for reflection, Holzapfel, dressed in the same blue tracksuit he wore when he was imprisoned by the communist regime, paced his cell on Thursday, delivering a broad-ranging commentary on human rights.
“This is just a small small part of what thousands of political prisoners suffered under the GDR but with the modern technology, we can convey to many people around the world some idea of what it was like,'' the 65-year-old said.
“Today, a 25-year-old has no experience of a state without justice.”
Hubertus Knabe, the scientific director of Hohenschönhausen, which is now a museum, said the display intended to temper the 20th anniversary celebrations with a sober reminder of just what the communist regime was like.
“They want to make clear that the happy end was not the whole story of the communist dictatorship, but there were 40 years of repression before it … and that the victims are still often suffering today because of what they experienced here and at other prisons,” he said.