This train has 23 tank cars full of sulfuric acid. It has left the Potrerillos copper refinery around 9:00 am. The plant is very close. It is just a matter of about 10 kilometers (6 miles). But when I shot this picture, it was already 9:30. Without moving, I was able to take more pictures for 12 minutes. The train moved so slowly that I had enough time to walk about 2 km (1.25 mile) to get back to my car, drive down to the bottom of the valley, and meet the same train again at 10h28 some kilometers east of where I had just took the picture that you see here (see picture 344640). The valley is narrow and the sight from the mountain on the opposite side is utterly amazing - take some time and have a look at Google Maps (weblink here below). This was one of the high points in my August 2010 trip in Chile.