The border crossing at Villazón, open between 5 a.m. and 8 p.m., is well organized and efficient. If you have all your papers in order then you will not have a problem quickly passing into, or out of, Bolivia. The Argentine and Bolivian immigration offices are situated within easy walking distance of each other at either end of a small bridge over a river that marks the border between the two countries. On the Villazón side, the immigration office is surprisingly well set up with two windows clearly labeled "Entry Stamp" and "Departure Stamp", helping to make the whole process extremely painless. Although, as with all South American border crossings, there are some dodgy characters and fake currency (Casa de Cambio Sucre, Av. Republica Argentina, is a reputable place to change money) to avoid--this is one of the continents easier places to switch country.