Al Mualim spends quite a bit of time in Assassins Creed I explaining to Altair about how he needs to "pierce the illusion" and how Assassins are trained to be highly perceptive, and how their creed is intended to make them wise and see the truth in all things. The real significance of this escaped this troper until he realized that Al Mualim was specifically talking about Eagle Vision, and how Altair uses Eagle Vision to literally pierce the illusions created by the Piece of Eden. - Unknown Troper
We tropers have turned Altair into a Memetic Badass, and while most of that is based on the game's attempt at justifying Regenerating Health, not all of it is. To wit, the synch bar's length increases as Desmond grows closer to Altair, by doing things Altair remembers doing. However, the synch bar does not increase when Desmond kills one of the sixty Templars. He can kill every Templar in the game without increasing the synch bar in the slightest. In other words, Altair may have killed every single Templar in the Holy Land, and he doesn't even remember it. Just another day at the office. (Of course, it could also be Fridge Horror if the senility that he showed during his final days in Revelations took those memories away).
Even if Altair forgot those memories, they would still be stored in his DNA.
There is an unflattering legend about the real Assassin Order that says that the members of the order indocrinated promissing young men into becoming assassins by taking them to a beautiful garden while they were under the effects of hallucinogenic drugs and then telling them that what they had just witnessed was Paradise itself, and that they could go live there one day if they did exactly what their mentors told them to. Apparently, that was the source of their suicidal dedication to the order. In-game, behind Masyaf castle there is a beautiful garden, which is also where the final boss fight takes place.
If you look at the memory log for the last mission, you'll notice that garden is actually called Paradise. Al Mualim also references this legend when you talk to him after Garnier's death.
You also see a hint of this at the very very very beginning of the game, when they try to drop Desmond at the last memory and it starts rejecting him. Altair is clearly in that garden and a group of (faceless) maidens are flocking around him. We're witnessing Altair's own indoctrination. Apparently the Animus pushed us to a much further back memory than we first anticipated.
This legend is actually mentioned in-game, and makes it clear that it's completely false.
Besides the fact that the farther back the Animus boots you, the clearer a memory would become.
For a while, Altair's voice bugged me. In the first game he's the only character in the animus who doesn't have an appropriate accent. At first I thought it was Desmond's voice, but it's not, it's a completely different voice actor. Why bother getting an American accent for Altair when everything else was made as historically accurate as possible? Then it hit me: it's Desmond's voice AS HE IMAGINES IT SOUNDS. This troper has a mild speech impediment and can confirm that your own voice sounds a lot different in your head then it does in real life, I always get a shock when I listen to recordings of myself speaking. To Desmond, his voice sounds more badass than it actually is, so when in the animus, he naturally has a cooler sounding voice.
The game was boringly repetitive for a reason. The designers wanted to show that no matter how cool a job may seem, it's still a dull routine after you keep doing it, day in and day out. A warning to people considering a potentially "cool" or "fun" career, demonstrating that even something as interesting as assassinations loses its entertainment value after seven or eight times.
Acre seems to be the worst off out of all the cities you visit, especially its poor district. Whole buildings have been damaged or completely destroyed. It is also the only city where you see dead bodies that were not killed by Altair. This was probably deliberate in order to demonstrate how the Muslim world was more advanced than the Christian world at the time and so would most likely have better sanitation.
It's much more likely to be damage resulting from the siege of Acre (in-game dialogue suggests that the game takes place in August 1191). Look at the approach to the city and you can see the remnants of siege machines surrounding it. The Poor district is nearest the gates, hence all the wrecked buildings that have had trebuchet boulders thrown through them. The devastation's probably caused by war, rather than poor sanitation (not sure that causes house to collapse!)
If you take too long in the battle against Al Mualim, he'll use an unvoidable attack to blind you. When this happens, you automatically begin to desynchronize. If that's the case, then that means Altair never got blinded. Curb-stomping Al Mualim with a counter from the hidden blade is what actually happened!
Considering the placement of all the major locations—Masyaf, Damascus, Jerusalem, Acre, and Arsuf—then the Kingdom must be mostly in Lebanon and northern Israel.