What is Game of Thrones map based on?

What is Game of Thrones map based on? Back in 2014, Game of Thrones author George R.R. Martin revealed that the fictional continent of Westeros is in fact based on an inverted map of Britain and Ireland, with Co. Kerry playing a starring role in the new world in an exact (albeit upside down) reproduction.

Back in 2014, Game of Thrones author George R.R. Martin revealed that the fictional continent of Westeros is in fact based on an inverted map of Britain and Ireland, with Co. Kerry playing a starring role in the new world in an exact (albeit upside down) reproduction.