Marmara Prison, the most secure prison in Europe, contains, among others, journalists and politicians who have criticized the regime of Turkey's President Erdogan.
One of the most well-known people in Turkey who was sent to prison is the ousted Mayor of Istanbul, Ekrem İmamoğlu, whose arrest sparked protests across Turkey.
The complex spans an area of about one square kilometer and was originally designed to hold up to 11,000 prisoners, but as of 2019, the prison held 23,000 prisoners.
The prison has become a symbol of Turkish oppression due to the fact that protesters and regime critics of the Turkish president have been sent there.
Adil Demirci, a social worker who was imprisoned there for nearly a year, told Deutsche Welle: "At first, I was placed in a cell in Block 9 and could only communicate with the neighboring prisoners through the door. That was the only way."
According to human rights organizations in Turkey, prisoners in the prison are kept in isolation with no ability to communicate with others as part of the prison's torture methods.
In addition, the organizations state that the prison ensures that enemies of Erdogan from different groups are kept together. For example, leftists are imprisoned alongside extremist Islamists.