Cuba currently refuses to allow the International Red Cross to visit its prisons.
It houses 57,000 prisoners in 200 facilities...but claims it is trying to reduce the population at its 5 maximum security prisons.
Political prisoners have long written about the atrocious conditions they suffered.
There are an estimated 92 political prisoners in prisons..and 350 held in short term cells.
The BBC's Sarah Rainsford describes a recent supervised visit to 2 prisons...including the notorious 3,000-bed Combinado del Este.