This is one of the location needed to find for the Garth Agarwen Exploration deed.
It is located in Lonelands far North-East of Agamaur inside the Garth Agarwen instance. Once inside the instance fight your way North-East until you find the Barrow's Gate.
To enter the Barrow's Gate you will need a key which I was told drops from a named wight, I have emptied the whole instance twice and still cannot find the correct wight. I was also told the named wights are near Ivar but everything I find says he is behind the Barrow's Gate so that cant be right. Someone mentioned it may be from one of the named wights in Barrow Downs but I havent checked yet.