The prospect of solitude drew the first Russians here. Early in the 15th century, two monks debarked on the island’s northern coast, seeking a place of religious retreat amid pristine taiga and bog. They initiated cloistral traditions that led, soon after, to the founding of Solovetsky Monastery. But almost from the beginning, the Solovetsky Islands were also abodes of exile and detention. The isolation and severe climate well suited the penal needs of an authoritarian state ruled by a czar. Monks both served God and acted as prison wardens. In the monastery’s darkest corners, they built cells that would hold a spectrum of prisoners, from the dissident gentry and errant clergy, to rebellious Cossacks and Decembrist revolutionaries.

I climbed stairs above the monastery’s granary and examined a few of the cells—low, vaulted brick chambers with tiny barred windows overlooking the desolate, churning Bay of Prosperity. The experience created by the monks was easily outdone when the Bolsheviks instituted a reign of sadistic terror that earned the Solovki infamy throughout the Soviet Union. Behind glass in one of the monastery’s chilly, damp corridors, an exposition of photographs and documents displays that regime’s grisly legacy—twisted corpses strewn across fields, stacked skulls, ransacked churches, smashed church bells, and orders of execution. In 1923, the authorities reconstituted the monastery-prison (and the rest of the island) as the country’s first concentration camp, designed to “rehabilitate” the most potentially dangerous “enemies of the people”—writers, poets, academics, and anyone else who fell afoul of the revolution. During the 1930s, when Stalin and Hitler enjoyed cordial, if wary, relations, German officers visited the island and studied its “correctional” regimen, gleaning elements that they would soon put to use on a far more horrific scale.

The macabre cruelties of all the Soviet gulags have been well documented, but even so, those of the Solovki stand out. Camp officials welcomed each group of arriving inmates by immediately shooting two prisoners dead, and pummeling the rest with shovels. Locked in unheated cells in the winter, the prisoners slept in piles three or four deep for warmth. Guards doused some in water and made them huddle for hours in the cold. Of the 80,000 Soviets condemned to the Solovki between 1923 and 1939, some 40,000 died here.

Finally, even for Stalinist authorities on the mainland, the Solovki’s unsanctioned atrocities exceeded the acceptable. In 1939, the camp was closed, and some of its administrators were executed. The remaining prisoners were moved to the mainland. As another tour guide, the historian Oleg Kodola, pointed out, “By 1940, the whole country had been turned into a prison camp. It made no difference which side of the barbed wire you were on.”