Lake Cassien or Lac de Saint-Cassien in france, home to many large carp and catfish, i would personally love to see this in game, it's a very large water body and would be perfect for a challenging lake to fish.
Well 8 to 1 in favour! for Lake Cassien, this lake has always intrested me ever since i read the "13 hour fight" in the book Carp the quest for the Queen, long story short the guy had a fish on for 13 hours and lost it.. never saw it so, Some saw it was either a miss hooked huge carp , catfish or a sturgeon. nice story and book though i recommend it.