Our first stop on the Uyuni salt flats tour was an abandoned train yard just outside of Uyuni itself. Given the proximity to the town it seems we could probably have walked here ourselves at some point and explored the trains with fewer people around (would be rad to come here at night time).
The trains themselves are mostly covered in graffiti and many have been modified in some way. A swing set on one of the beams between two trains was fun.
We only spent about a half hour at the train yard before we headed back to Uyuni for our next stop: the salt flats!