In Allinge, Bornholm, Denmark there are remains of what once was a two rail railway in the harbour. The railway joined "Allingebanen" which was one of the three main railways on Bornholm (now closed).
The railway that went to the harbour is still clearly visible. The embankment just outside the harbour has become a cycle and walk path. On the actual harbour you can clearly see where the two rails were (see thumbnail). The harbour's docks are made from cobblestones and where the two rails where they have now placed some other from of stones.
The link shows an areal view of Allinge Harbour from the time when the railway was still active. The rails are to the right of the picture.
http://jernbanen.dk/forum2/images/uploaded/20120721153246500acb9e8a570.jpg