Was Modern Chess Invented in Valencia?

I came across an interesting article yesterday, in a blog post advertising a rematch between chess grandmasters Kasparov and Karpov, due to take place next week in Valencia. Apparently, signs are appearing in the city that claim Valencia was the birthplace of modern chess. Is this really true? It surprised me, and the writers of HolaValencia.net too, who decided to do a little investigating. And they found this: Valencia and the Origin of Modern Chess.

So if you're visiting Valencia sometime soon, what better souvenir than a chessboard from the game's birthplace?