On a recent trip to the Isle of Skye we took a hike to a remote peninsula and found some curious workings. After bumping into a local enthusiast and a bit of Googling we discovered it is a very old canal.
It turns out that it was built by Vikings and connects the sea with a small loch. The loch would have been used to repair Viking ships and the Vikings would have hauled their long boat from the sea to the loch for repairs.
There were lots of bits of stone buildings, tumuli and caves scattered about, so possibly there was an old Viking settlement there too. Some newer stuff as well but nothing recent.