Odd Artifact

This is, apparently, a Dog Head Spike.
Those of us old enough to remember the ancient TV series "Casey Jones", about an American railwayman (railroader) in the 19th century, will appreciate what this is for. For most of us, it is a kind of huge nail which was hammered into the wooden sleepers to hold the rails in place.
This one came from the line of the Otago Central Railway. Part of this line is still open as a tourist line and is well worth a visit (the Taeri Gorge Railway) but the rest is now closed and converted to a cycle/walking trail.
An unusual memento of a great visit: it makes me think of old steam engines thundering up the valleys from Dunedin to Cromwell and the huge effort needed to drive the railway through these hills.