You need to solve the simple puzzle to get the coordinates for the cache location.
The final location is in a very high muggle area and you will need to be stealthy.
The cache can be found at......
N51 Eight Hours . Mutiny ( Door Number 3 + Brazil )
W000 (Compass - Grace) . ( Space Oddity - Exodus ) ( Molon Labe +Silent Kill )
when you have solved the puzzle and checked your answer please add 4 to your last digit on Northings and Add 2 to your last digit on Westings ie if your last digit is 1 add 4 to make 5 . This has been done to make your search of GZ more accurate. Feel free to message me if needed