On Christmas day, we head to the train station for our ride back to San Francisco - the part of the trip I have been looking forward to the most - the rail journey over the Sierra Nevada.

As we wait for the train to arrive from Chicago, we watch a colony of cats playing around an Air Monitoring Station, which looks suspiciously like a trailer from a 1950's Duck & Cover nuclear war movie.  Someone who works in the windowless trailer with it's protruding radiation monitoring equipment has built houses for the cats.  Every time we think we have counted all the cats, another one ambles out from under the trailer.