Puzzle 55: Mynydd Graig Goch

Note: I won't lie to you. I have to nominate this as the hardest puzzle to date. If you can crack this one, give yourself a pat on the back because it is one of the toughest puzzles online.

For more than a century, Mynydd Graig Goch, in Wales, was considered a mere "hill". But in 2009, that changed when local enthusiasts using state-of-the-art equipment were able to prove that the highest point actually does exceed the 2,000ft requirement.

Guardian: The Welshmen who went up a hill, but came down a mountain