Please read my license notice before copying my photos.
The longest train trip I ever took was Hong Kong to London. It was not continuous and took over a month, but it was all by train except for a short stretch by bus in Germany. I had landed in Hong Kong having fled a coup attempt in Manila. Then I heard that the Berlin Wall was being torn down and hopped on the next train. The longest stretch was the Trans-Mongolian from Beijing to Moscow. That ticket cost US $45. We stopped at the border between China and Mongolia to have the bogies changed from standard to Russian gauge. I will add more detail when I am able to refer to my notes.
Jim Rees