Robert the Bruce extended a castle located on the southern shore of which Loch ?
Tarbertshire:  It has been suggested that Robert the Bruce, who extended Tarbert Castle, created or intended a sheriffdom there; however, the first reference to Tarbertshire is in 1481, when Knapdale (back then including the lands between Loch Awe and Loch Fyne) was transferred to it from Perthshire. Tarbert Castle: Tarbert Castle is located on the southern shore of East Loch Tarbert, at Tarbert, Argyll, Scotland, at the north end of Kintyre.
East Loch Tarbert