They are images of Soviet Russia that its secret service did not want the world to see.
Now, however, an archive of photographs taken by the pioneering photographer Margaret Watkins are at the centre of a new exhibition in Glasgow, where she was based.
Watkins, born in Ontario in Canada in 1884, learned photography in the US but moved to Glasgow to get away from her home in New York, staying with an aunt in Westbourne Gardens, in the city's west end.
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While based in Scotland, the photographer – currently being celebrated with an exhibition at the National Gallery in Canada – visited post-revolutionary Russia and Moscow, and fell foul of its secret service in 1933.
The images she managed to bring back to Glasgow are now partially on show at the Hidden Lane gallery in Glasgow until February next year.
Watkins – in Moscow through the invitation of Intourist, the state agency charged with bringing visitors into the new Soviet country – was arrested by the OGPU, the predecessor of the KGB, after photographing one particular block of flats which concerned them.
Her camera and films were confiscated, and after interrogation she was released.
However, Watkins, who died in Glasgow in 1969, managed to sneak 600 negatives out of Russia, along with more that were officially approved by the Soviet government.
The negatives are now on show at the Glasgow gallery, most of them printed for the first time as silver gelatin prints, made by Glasgow master printer and photographer Robert Burns.
The owner of the Hidden Lane gallery is Joe Mulholland, who discovered the extraordinary cache of photographs of Ms Watkins, who was his neighbour, when she passed away.
He said: "Few, if any, know she had been a photographer.
"No-one was aware she had achieved fame in New York, as a peer of many who later emerged as pioneers in the development of pictorial and modernist photography."
While immensely proud of the show at the National Gallery of Canada, Mr Mulholland said: "Perhaps now, the second leg of my dream for Margaret Watkins can be realised: a show at the National Galleries of Scotland in Edinburgh, a project mooted by me 30 years ago that accomplished, would mean I could rest on my laurels."