The border crossing between Austria and Liechtenstein is done by climbing a few "steps" after the bridge over the Samina. Plan to carry your bike and may be unsuitable if you have difficulty walking, but the effort is brief.
Over a few steps and a small, wooden bridge and suddenly you stand on Austrian or (depending on the walking direction) Liechtenstein soil. A turn that one does not expect at all in the middle of untouched nature. 😊