Personally I hate these huge pages of links. I never know where to start. If you are not like me, just skip down to the huge list at the bottom of the page. If you are like me then let me guide you through. Just click an interesting topic as it appears in the overview, and when you have read enough there, come back here to get more.
(Please keep in mind that untill the game is out, many of the following links may never have anything to do with GK3, but then again.....)

Overview:

Gabriel Knight 3: Blood of the Sacred, Blood of the Damned takes place in a small French Village of Rennes-le-Château.
www.rennes-le-chateau.com is undoubtedly the best, and most complete site for Rennes-le-Château information. It is written in English, French or German.

Many mysteries and rumors of treasure surround this small village. The most popular is the story of the small parish priest and the scrolls he found hidden in his very strange church.
The societies and groups who have lived in the area over the centuries contributed to the mysterious history of Rennes-le-Château. Several of these groups are the Cathars, the Visigoths, and the Templars. Some even speculate this treasure to be the Arc of the Covenant, or the Holy Grail.
You can even go on a treasure hunting vacation in the area.

The Holy Grail itself is a mystery. One that has fascinated an old friend, or should I say the great-great-grandson of an old friend: Richard Wagner. Adrian Wagner wrote the article and the music here.
The Grail has also been speculated to represent the bloodline of Jesus. It has been hypothesized that Mary Magdalene was the wife of Jesus, and that their descendents are still alive today, and intermarried with many of the royal bloodlines of Europe. This secret lineage may have been guarded by a secret society called the Prieuré de Sion (or the Priory of Sion).
You can even take a virtual tour of the Grail Mystery and receive recognition if you answer his riddle.

The geometry of the ancient and modern buildings in the area and the Paris meridian form an elongated pentagram which may relate to ancient Egyptian creation myths, and sacred geometry. The Egyptian goddess Isis is closely tied to the area and to the Prieuré de Sion.

Politically the Templars are tied in with the Illuminati, and have had direct confrontations with the church (Vatican). What ever became of the Templars?

And of course what fun would Gabe have if there wasn't an occult connection so you may want to read up on vampires here, here,and here.
Another interesting character is Vlad Tepes (or Vlad the Impaler) he was the historical person used for the fictional Dracula character.
Jane Jensen has said hers will be different, more like alchemists.
Jane has also said she was influenced by Anne Rice, and Stephen King.


Categorized Links:

THE CATHARS

THE GRAIL
THE PRIEURE DE SION
RENNES-LE-CHÂTEAU
THE TEMPLARS
VAMPIRES
VISIGOTHS