Finding the Garden of Eden

Finding the Garden of Eden is the tenth main quest in Fallout 3. It is also a PlayStation 3 trophy and an Xbox 360/PC achievement.

Enter Vault 87
Depending on your choice during Picking Up the Trail, you either have to fight your way through Murder Pass to the vault door and enter or talk to Joseph in order to hack the terminal to enter Vault 87.

Find a G.E.C.K.
Both entrances of Vault 87 lead to the Reactor Chamber. From there, you proceed to the Living Quarters, then the Test Labs. There, you eventually encounter and liberate a Super Mutant named Fawkes who asks to hold a conversation with you over the intercom. Fawkes explains his upbringing in the vault and how he has become intelligible and civilized through continued access to the vault's database. Fawkes promises to retrieve the Garden of Eden Creation Kit from the irradiated halls above if he is released.

The radiation level where the G.E.C.K. is stored is extremely high. You can proceed in one of two ways:
 * Attempt to get the G.E.C.K. without help. If you choose to do so, sufficient protection will be needed to resist the radiation and/or some RadAway. There is an advanced radiation suit in a locked storage room on the way to the G.E.C.K.
 * Release Fawkes, who will assist you in both combat and obtaining the G.E.C.K., thus fulfilling the objective of the quest. See free Fawkes below.

The room with the G.E.C.K. can be found by going left from Fawkes' cell. If you release him, he slowly leads you to it and will engage the remaining enemies in melee. Fawkes is even tougher in this part of the game than he is as a follower, so you shouldn't worry about him dying.

Optional: Free Fawkes

 * Upon your arrival at his cell, Fawkes will ask you to unlock his door somehow. An option that he provides is triggering the test area's fire alarm, which will explosively release all of the chamber doors, and the subjects within. To avoid the battle after triggering the alarm, it is possible to hack each Hard terminal next to the occupied rooms (see below) and trigger the command "terminate subject," which will instantly kill them in a jet of fire. Whether you choose to do this or not, you need to go down the hall to the right. At the back of the last room, there is a fire control console here that can be activated to unlock all of the cells or an average computer terminal next to it that can be hacked to open his cell directly (he is in room 5). Isolation Room 5's door cannot be picked, and using the chamber's local hard terminal to unlock it yields a message saying the door is jammed.
 * The rooms contain:
 * Isolation Room 01 - Three dead people (two wastelanders and one raider).
 * Isolation Room 02 - Vacant (centaur possible).
 * Isolation Room 03 - The only "dangerous" test subject, a nutty human named Sid. If you unlock the door through picking the lock, he may be spoken with, where he will babble insanely, including how everyone is dead and "it's all his fault," and to "get out of his head." If the door is unlocked through the terminal (be it his or the master one) or the fire control, he will turn hostile.
 * Isolation Room 04 - Vacant (centaur possible).
 * Isolation Room 05 - Fawkes.

Once Fawkes is free, he will thank you and hold up his end of the bargain. He will proceed to slowly walk to the room with the G.E.C.K., fighting any enemy super mutants along the way. Once he's there, talk to him again to get him to retrieve the G.E.C.K. He can be watched through the windows as he does this, or alternatively followed (talking to him during this will yield an amusing comment). If you do not feel like waiting for him in real-time, a two-hour wait is enough to bring him instantly back to you.

However, if Fawkes is killed, the player character will have no choice but to retrieve the G.E.C.K. on their own. Fortunately, Fawkes is extremely tough - practically invincible - so the only way you'd find yourself in that situation is if you intentionally killed him yourself. If, after retrieving the G.E.C.K., Fawkes is engaged and killed before handing it over to the player character, it can be looted from his corpse.

Escape from Vault 87
After all this effort you will be incapacitated upon attempting to leave the Vault by a type of flash bang grenade, and Colonel Autumn will show up with some Enclave soldiers, and take the G.E.C.K. from you. You will pass out a few moments later. An exception to this is in the bugs section below.

Followers
If you are accompanied by a companion, they will not be with you after you have been incapacitated by the Enclave. Be sure to retrieve any equipment from them you do not want them to walk off with (as if they were fired) before this happens, or right after retrieving the G.E.C.K. You will not have a chance to re-hire your companion until after The American Dream. After re-hiring a companion they will have all the items you left with them still in their inventory, so it can be a good way to free up inventory space of non-essential items you want but won't need during your time in Raven Rock, allowing you to stock up on the mountains of Enclave gear.
 * Butch DeLoria will return to The Muddy Rudder in Rivet City. Butch will not follow you if your Karma strays from Neutral.
 * Charon can be found at The Ninth Circle in Underworld immediately after escaping from Raven Rock. You can take him back for free (you still hold his contract) and, of course, regardless of your Karma. When you engage a conversation with him he will speak to you as if you had asked him to wait for you ("You return. Shall I join you once again?").
 * Star Paladin Cross will return to the Citadel and can be rehired as long as your Karma is good; otherwise she will refuse to join you.
 * Dogmeat will be waiting in front of Vault 101, but be warned that he may die before you take him back.
 * Clover will be back in Eulogy's house in Paradise Falls, even if you killed everyone in town, including Eulogy. You can take her with you without having to pay and regardless of Karma (as a slave she is blindly loyal).
 * Sergeant RL-3 will be waiting for you at Canterbury Commons. You do not have to pay to take him back, but your Karma must remain neutral.
 * Jericho will be in Megaton, most likely Moriarty's Saloon. If Megaton is destroyed he will wander around the ruins. If your Karma is now too high for him (neutral or good), he will refuse to follow you again.

A good way to regain lost items from your followers is to sneak attack them with the Victory Rifle and take your stuff while they are down. This has no loss of Karma, nor will the ex-followers turn on you. You cannot take the armor off. This is useful when you had two followers from different Karma zones, and do not want to commit Karma giving deeds to reclaim your items.

Behind the scenes
The name of the quest is a play on words: not only that the player character searches for the Garden of Eden Creation Kit, but the quest also ends in finding the residence ("garden") of Eden.

Bugs

 * It is possible that while talking to Fawkes, the game may freeze and you will have to reset your console.
 * While following Fawkes to retrieve the G.E.C.K., you can talk to him with a standard set of follower conversation options and trade equipment with him. However, after he gets the G.E.C.K. for you, the talk options are not available anymore - you lose anything you gave him. The next time you see him outside of Vault 87, he will have an empty inventory.
 * Fawkes may get stuck between a wall and a machine for a while when walking to the G.E.C.K. If that happens, the player can give him a shove to help get him out.
 * Even though Fawkes may be near "invincible," if the player moves through a path Fawkes cannot follow (over a ledge, jump, etc.) when first leaving Raven Rock, the player will hear Fawkes' Gatling laser-firing continuously and Fawkes may die. Upon investigation it seemed he was killed by a lone yao guai. This happened when traveling over a rock ledge to the southwest of Raven Rock.
 * For some reason you may be able to hear Dogmeat's panting during the cutscene.
 * It is possible when exploring Little Lamplight prior to initiating this quest that the Reactor Chamber door which is normally locked will be unlocked. This allows the person to explore Vault 87 and even acquire the G.E.C.K. (or two), Fawkes, and the Enclave ambush. Quest completion and achievement follow suit.
 * If you have Star Paladin Cross as a follower when getting captured, she might vanish from the game entirely instead of being back at the Citadel. It may also happen with other followers (i.e. Clover).
 * If you agree to rescue Fawkes, and yet leave him within his cell and obtain the GECK yourself, the game checks the objective "Optional: Rescue Fawkes" as complete, even though you end up going to Raven Rock while he is contained.
 * If you choose to activate the G.E.C.K. rather than taking it, the pulse that emits from it will, rather than killing you, stun you indefinitely, leaving you to die slowly from radiation poisoning (unless your unconscious body lands in a non-radiated space, in which case you will remain lying on the floor forever).
 * It is possible that the G.E.C.K. will not be removed from your inventory when you are captured by the Enclave. This does not interfere with the storyline and the next quest occurs as if the Enclave had taken the G.E.C.K. But, as the G.E.C.K. is a quest item, you cannot remove it from your inventory without the use of the console command.
 * If the Lone Wanderer leaves Vault 87 after agreeing to free Fawkes, upon returning, Fawkes might be in his isolation room with the centaur from Isolation Room #4.
 * If you don't activate the alarm and then pick up the G.E.C.K, the cutscene will never trigger while leaving Vault 87. The leave Vault 87 objective will never be completed.