on the secrecy of the construction of Baikonur: there was a correspondent in the first construction team in the newspapers a list of labor exploits of youth was published 243 people received awards
(I found the story with the CIA in the "yellow press")
after his flight, Yuri Gagarin holds a press conference (for the foreign press) where he talks in detail about his flight
And still, they placed the construction site 300 km east than it really was. Again, read the article, it is pretty good and often quoted.