Rudolf Hess was the only inmate in Spandau Prison.

Spandau Prison was a prison situated in the borough of Spandau in western Berlin, constructed in 1876 and demolished in 1987 after the death of its last prisoner, Rudolf Hess, to prevent it from becoming a neo-Nazi shrine. The prison was near, though not part of, the Renaissance-era Spandau Citadel fortress. In history, Spandau Prison succeeded as a prison to the citadel and where Frederick II of Prussia had held captive the magistrates of the Prussian Kammergericht and the Spandau gaol, where Carl Schurz had freed his friend Gottfried Kinkel in the aftermath of the 1848 German revolution.^[1] The magistrates and Kinkel were held captive as Festungsgefangene (fortress prisoners), being privileged in detainment conditions.
The prison was built in 1876. It initially served as a military detention center. From 1919 it was also used for civilian inmates. It held up to 600 inmates at that time.
In the aftermath of the Reichstag Fire of 1933, opponents of Hitler and journalists such as Egon Kisch and Carl von Ossietzky were held there in so-called protective custody. Spandau Prison became a sort of predecessor of the Nazi concentration camps. While it was formally operated by the Prussian Ministry of Justice, the Gestapo tortured and abused its inmates, as Egon Erwin Kisch recalls in his memories of Spandau Prison. By the end of 1933 the first Nazi concentration camps had been erected (at Dachau, Osthofen, Oranienburg, Sonnenburg, Lichtenburg and the marshland camps around Esterwegen); all remaining prisoners who had been held in so-called protective custody in state prisons were transferred to these concentration camps.
After World War II it was operated by the Four-Power Authorities to house the Nazi war criminals sentenced to imprisonment at the Nuremberg Trials.
Only seven prisoners were finally imprisoned there. Arriving from Nuremberg on 18 July 1947, they were:

• Rudolf Hess - serving a life sentence (died 1987)
• Walther Funk - serving a life sentence (released 16 May 1957)
• Erich Raeder - serving a life sentence (released 1955)
• Albert Speer - serving a 20 year term (released 30 September 1966)
• Baldur von Schirach - serving a 20 year term (released 30 September 1966)
• Konstantin von Neurath - serving a 15 year term (released 1954)
• Karl Dönitz - serving a 10 year term (released 1956)

Of the seven, only four fully served their sentences; the remaining three, Neurath, Raeder, and Funk, having been released earlier due to ill health. Between 1966 and 1987, Rudolf Hess was the only inmate in Spandau Prison. His only companion was the warden, Eugene K. Bird, who became a close friend. Bird wrote a book about Hess's imprisonment entitled The Loneliest Man in the World.

In the aftermath of the atrocities, committed by these men and men like them, it is hard to imagine that prison was the best choice for their punishment.  Six million Jews killed by ways and means that are hard for us to even begin to imagine, scores of others died fighting in a war against lunatics and those who surrounded them.
What causes a society to lose its mind?  Where do we find humanity in any of this?  I am certain there were those in the Third Reich who knew Hitler was on a course of certain disaster, but why did they go along?  Why acquiesce to the will of an evil dictator?  Mass delusion is powerful.  Even today we see strands of this type of behavior among certain dictators.