The messages, most written in 1967 to mark the 50th anniversary of the revolution, expressed envy for comrades of the future and confidently predicted triumphs such as landing on Mars.
"How are we celebrating the country's anniversary?" asked one letter dug up in the Siberian city of Krasnoyarsk, the tabloid Komsomolskaya Pravda reported.
Those writing the messages did not know that by 2017, the Communist Party's rule would have ended nearly three decades earlier in 1991.
At a school in the far-eastern Blagoveshchensk region, children and elderly residents opened a rocket-shaped capsule, a local news site reported.
A handwritten scroll from 1967 predicted that future generations would build "beautiful palaces".
"All that we did, we did so that you today would feel all our devotion to the country, the people and the Party," it said.
"Be as we imagine you."
A capsule from 1977 at a school in the Siberian city of Omsk contained recordings of Lenin's speeches and a book by Leonid Brezhnev, the country's leader at the time, Komsomolskaya Pravda reported.
The Soviet Union sent the first person into orbit in 1961 and the excitement of the time over space travel is evident in the letters.
A message from 1967 left in Serov, in the central Sverdlovsk region, predicted the town would have "a launch base for supersonic passenger rocket-planes".
More prescient, it said people would have "colour televisions and video phones," the local news site Skazhur reported.
The authors wrote: "We envy you a little! The young generation of the Communist future!"
Ilya Varlamov, a popular blogger, posted a message from a time capsule in Siberia's Novosibirsk region, adding it made for "sad" reading.
"We believe that you have... settled on the moon and landed on Mars," the three-page typed letter says.
It predicts "your spaceships have long crossed the galaxy" and "you're holding talks on scientific and cultural cooperation with other, alien civilisations."
November 7, the date marking the start of the revolution, is no longer a national holiday, and the Kremlin has not held any official events to mark the date.
According to local media a message in the western city of Kursk read: "We infinitely envy you, our comrades and descendants."
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