The Mysterious Wall (1967)

Original title: Таинственная стена

The action takes place in Siberia where a mysterious wall appears from time to time. Scientists are dispatched to study it and some of them believe that the wall is produced by some sort of alien intelligence, "the Martians", as they call them. The scientists attempt to communicate with the Wall, but all they experience in return are hallucinations about their past experiences. In those visions they are faced with some unresolved issues, repressed memories, and absurd dream-like situations. They meet people – messengers – from their past who reveal to them some simple truths about their own lives, which may be hard to accept, so they dismiss those messengers as the Martians and stubbornly continue attempting to "understand" the Mysterious Wall using their rational minds.