Yesterday, someone came to me and told me that he had found a treasure map. I told him that it was just a map of France, but he insisted that there was something with this map that could lead us to one of the greatest treasures of France, because he found it in a map with important documents for his entire family. However, we had no clue where to start.
Can you help us finding the treasure?
If you have found anything useful, you can post an answer.
Hint:
You can find text in the image. If you don't know how, but you want to know, see the community wiki answer. This text is encrypted with Vigenère chiper and the key consist of three English words that shouldn't, given the image, not be to hard to guess. Also, the flag is just to make sure that everyone sees that it is France.