What I know about the man who you told me yesterday is that he has just retired from factory that/which I visited two days ago.
其中What I know about the man who you told me yesterday是主语从句,从句中who you told me yesterday是定语从句,先行词是the man.
that he has just retired from factory that/which I visited two days ago是表语从句,表语从句中that/which I visited two days ago是定语从句,先行词是the factory.
当然,这是编的．可以根据实际情况而用相应的从句．