Trains in Chile:

Chile - Bolivia:
There is a train between Uyuni in Bolivia and Calama in Chile. Although there are better ways to travel between the two countries, like a trip between San Pedro de Atacama and Uyuni, this train offers one of the rare occasions for enthusiasts to travel between two countries in South America. It leaves once a week and should take about 24 hours, although delays are not unheard of. Bring sufficient food and drinks and some warm clothing as temperatures plumid during the night.

Chile - Argentina:
Although it is not an international connection, the Tren de las Nubes (lit. 'train of the clouds') connects the city of Salta in northwestern Argentina with the border of Chile high in the Andean mountains. The train leaves once a week and takes about 15 hours to complete the whole journey. Due to several problems the train hasn't been running for a few years, but service is scheduled to be resumed in 2008.