Last time I was on Scalpay I spent four nights at Dail-na-Mara, a B&B on Scalpay's North Harbour. On the shore below the house was a massive, derelict barge that appeared to be made of cement. It was quite an eyesore, but was making itself useful as a jetty and storage area for the local fishermen.
Later I would learn that this no longer afloat boat was the Cretetree, a 180-foot-long concrete barge built in 1919 for hauling iron ore. (The first five letters of her name come from her con-crete construction.) Cretetree's working life as a transport ended in 1953, and somehow they got her to Scalpay in 1955. That's 60 years now, and she's so solidly built she'll probably be there for another 60 years. See this RCAHMS page for more on the Cretetree.