Mt Tam is a California State Park unit. The old RR right of way are hiking and biking trails currently.. It was known as the crookedest RR in the world.. Gravity cars carried folks to the bottom without an engine...
check this vid out..http://www.youtube.com/watch?v=GJg-Zzd589Q
I lived there in the '50's and my wife worked for St Parks for several seasons more recently there.. a great number of car commercials you see on TV are filmed on their roads..
the building at the top was used for many things, currently a fire lookout..
sit back and enjoy this vid also..on full screen..https://vimeo.com/48169212