We love crossing borders, especially the international boundary experts among us.  Here we are about to cross the Mekong River from Laos to Thailand.  Mostly we have flown across borders (as in the airport photo below) with the exception of the crossing from Nanning, China to Hanoi, Vietnam by night train when we were awakened twice in two hours to exit the train with all of our luggage and deal with customs and immigration on both sides of the border.  Needless to say, the daytime crossing of the Mekong by boat was much easier.