Golden Doors are new to the series, first appearing in Fable III. There are four Golden Doors, and each can be opened by a Golden Key.
Hero of Bowerstone's tomb Golden Door
This Golden Door can be accessed through the Hero of Bowerstone's tomb. The hero's first encounter with this door is during the exodus from Bowerstone Castle during the first part of the game but is unable to be accessed until the hero collects a Golden Key which can be found later in the game. After opening this door you follow the path downwards and will run into a random party of monsters follow the path to the left and go up a rock spire at the top of the spire is a chest with 40 guild seal points inside.
Sunset House Golden Door
This Golden Door is located in the woods to the right of the Sunset House as you pass through boundary fences. You do not need to complete the Sunset house sidequest to gain access. A chest with Sorrow's Fist is found beyond the golden door.
Brightwall Academy Golden Door
A third golden door exists in the "dungeon" of Brightwall Academy where several quests occur. Close to the locked Silver Door (requires a key from Saul's quests) there is a Flit Switch which leads to several more Flit Switches, ending in the central atrium. Eventually a floating platform will arise and you will have to step on the annoying arrows about 20 times while fighting Hollow Men until the platform creates a winding staircase all the way down to a Golden Door. Inside, for all your time and effort, is the Highwaymen Men's and Woman's full suits, which cost about 20,000 gold in a clothier shop. Its "swashbuckling" good, and gives you high attractiveness ratings.
The Ossuary Golden Door
This door is in the Ossuary dungeon area. This area is unlocked during Gone But Not Forgotten, which is unlocked by doing Bored to Death in Mourningwood. Upon entering the area you will have to ascend a flight of stairs and run along the top to reach the other side of a chasm. Halfway across this balcony area, you'll clearly see the door on your left. The inside is filled with coffins, go up the stairs and there is a chest with a random Legendary Weapon.