 Old Castle Lachlan lies on the eastern shore of Loch Fyne , near Newton . The ruinous castle dates to the 15th century , and lies about 70 feet ( 21 @.@ 3 m ) north to south , 54 feet ( 16 @.@ 5 m ) east to west , and at its highest point 43 feet ( 13 @.@ 1 m ) high . 
