I was in a game, so I decided to claim the Machu Picchu because its effects were interesting but I realized afterwards that there was absolutely no moutain at all on the map, which led me to seek if I could unclaim it (given it was mathematically impossible to build) and I saw there was no option to unclaim a wonder so I'm stuck for the rest of the game with no alternative. I hope it's not voluntary and that it may prevent any other player or AI to face such a problem. 

And in my opinion, the game should have a boolean on the wonder pool to seek if it's possible to even build it in the first place (before showing it to the player) or make procedural rules that makes every wonders buildable, there are many options if it's unintended and I hope my solutions may help.