I'm very confident that the Pearl station is not the ?. Here's why.

1) From the Orientation video, it's clear that the residents of the Pearl are not high ranking members of the orientation, and they don't "need to know" anything. Not even the motivation of the residents of the Swan. The Pearl residents are as much a part of the experiment as the Swan residents; they are all rats in the maze. And when they put their messages in the tubes, they go "directly to us" - directly to DHARMA management. Which is located somewhere else on the island. And it would be really mean not to have that marked on the map, wouldn't it?

2) On the map, details about each of the hatches are written at the sides, adjacent to the relevent hatch. "The Pearl?" is written next to C4 on the right. The outline of C4 is dashed to indicate that the mapmaker doesn't know exactly where it is. However, it's quite clearly a seperate entity to the big ? in the middle.

3) The orientation videos say "Part X of 6". So there are 6 hatches. If ? is the Pearl, which is clearly a normal hatch, then the map shows 7 normal hatches, each presumably requiring an orientation video. It doesn't make sense. So ? isn't the Pearl. C4 is.

4) In between the Swan and the big ? on the map, there is.... another little "?". It would be very careless to put it there for no reason, wouldn't it? Perhaps what Eko discovers to be marked on the ground is this smaller "?".

5) But in fact, the marking on the ground doesn't look that much like a ? to me at all. It looks like a circle, which is the logo of the Pearl.

6) Next to C4, the mapmaker writes "HIGH POTENTIAL FOR R.V.S. FACILITY" - remote video surveillance.

7) Eko's brother mentioned there would be distractions...

whaddayasay

I agree completely.

I just realised the best proof of all:

8) Next to the big "?", the mapmaker writes, "DESIGNATION UNKNOWN, PURPOSE UNKNOWN". But, he knew (or at least suspected he knew) both the designation and purpose of the Pearl - he wrote them down next to C4! So, the Pearl is not the big "?".

But if the mapmaker knows where the Pearl is located, then why is the Pearl actually located on the island where the little ? is located on the map.

The mapmaker didn't know where the Pearl was located. That is why the outline of the C4 structure is dashed, and is labeled "C4?". He was making an educated guess.

But if the mapmaker knows where the Pearl is located, then why is the Pearl actually located on the island where the little ? is located on the map.

it isn't. eko and locke set out in the direction of the ?, but they camped over night at the drug-plane site to 'wait for further instruction'. that's when locke had the dream and eko found the circle in the grass.

they even specify before they camp that the map isn't exact and they don't even know what the geographical features on it represent. "they're squiggly lines," says locke.

Think of the spot on the map where the Pearl is supposedly located. If it's not really there, then what is in that spot? Just empty space?

I'm very confident that the Pearl station is not the ?. Here's why.
1) From the Orientation video, it's clear that the residents of the Pearl are not high ranking members of the orientation, and they don't "need to know" anything. Not even the motivation of the residents of the Swan. The Pearl residents are as much a part of the experiment as the Swan residents; they are all rats in the maze. And when they put their messages in the tubes, they go "directly to us" - directly to DHARMA management. Which is located somewhere else on the island. And it would be really mean not to have that marked on the map, wouldn't it?
2) On the map, details about each of the hatches are written at the sides, adjacent to the relevent hatch. "The Pearl?" is written next to C4 on the right. The outline of C4 is dashed to indicate that the mapmaker doesn't know exactly where it is. However, it's quite clearly a seperate entity to the big ? in the middle.
3) The orientation videos say "Part X of 6". So there are 6 hatches. If ? is the Pearl, which is clearly a normal hatch, then the map shows 7 normal hatches, each presumably requiring an orientation video. It doesn't make sense. So ? isn't the Pearl. C4 is.
4) In between the Swan and the big ? on the map, there is.... another little "?". It would be very careless to put it there for no reason, wouldn't it? Perhaps what Eko discovers to be marked on the ground is this smaller "?".
5) But in fact, the marking on the ground doesn't look that much like a ? to me at all. It looks like a circle, which is the logo of the Pearl.
6) Next to C4, the mapmaker writes "HIGH POTENTIAL FOR R.V.S. FACILITY" - remote video surveillance.
7) Eko's brother mentioned there would be distractions...
whaddayasay

Interesting PG, but I think the pearl station is the '?", and here's why:
1) The participants in the pearl are observers for a scientific experiment. By minimal standards, any decent experiment requires a double blind study if possible, whereby the subject and the observer are both blind to the true purpose of the experiment. This minimizes any biases and would stand up to scrutiny.

2) Many things on the blast door map are written on the margins of the map. As if they are just notations for thought that have no place in the map yet. Whoever drew the map, knows of 'the pearl' station, but not necissarily its where abouts, nor the purpose... so indicated by the big "?" in the circle. As in 'we' know there's some hatch in the centre, but we don't know what it does or it's name.... And we scribble down the 'pearl' on the side because we know there is one, but don't know where yet.

3) The 'Arrow' is not a hatch, rather a storage bunker.. thus, why it had nothing really in it. No computer, no living quaters, no orientation video.

4) the little ? is right at the end of one of the hatch corridos that have been blocked. Perhaps the little ? suggest whoever drew the map wants to know what that particular corridor leads to. After all, Sayid found one corridor that was poored over with feet of concrete, leading him to mention, the last time he saw something like that, was in Chernobyl.

5) The big circle is part of the ?, hence why the hatch door is on the bottom below the circle and under the plane.

6) Again, whoever drew the map knows, or believes that the pearl is where RVS takes place, if RVS even stands for 'remote video surveillence'. They are just don't know where yet.

7) Eko's brother led both Eko himself and Locke to the pearl.. and hasn't done anything since.

But then again, I could be wrong. :)

I agree completely.

I just realised the best proof of all:

8) Next to the big "?", the mapmaker writes, "DESIGNATION UNKNOWN, PURPOSE UNKNOWN". But, he knew (or at least suspected he knew) both the designation and purpose of the Pearl - he wrote them down next to C4! So, the Pearl is not the big "?".

And the antithesis to your 'best proof'

8) Unlike all the other known hatches (the swan, the staff, the flame, and the storage facility the arrow), their TITLES WERE WRITTEN ON TOP OF THE HATCH. Whereas, The Pearl and it's possible descripton are written beside a 'CV4?' hatch. Almost like a mapmake didn't know where The pearl was going to go yet? Hmmm.
100%
I agree completely.
Roland. Who do you agree with?

3) The 'Arrow' is not a hatch, rather a storage bunker.. thus, why it had nothing really in it. No computer, no living quaters, no orientation video.

The "Arrow" could be a storage bunker, but since we do not know the true layout of that bunker, I would also wonder if that location had blast doors and if they could have been down. Some of the interior was trashed and run down looking, but so was the "Swan" hallway leading from the hatch area.

I've also kind of wondered why only one out of four bunkers so far have been shown to have been fully supplied, maintained, and manned.

I know the "Arrow" bunker has been shown to have been abandoned, but why, and is it really (possible blast doors)?
The "Staff" bunker was shown earlier with "the others" inside, but no one is manning it now.
The "?" bunker was manned, but now whoever was there is gone, and why is not important to monitor the bunkers from there anymore?

The "Arrow" could be a storage bunker, but since we do not know the true layout of that bunker,

This argument was made as an antithesis to Pretty_G's reason why there are now seven hatches, but only six videos conceded.

As for you questions, interesting.. we'll have to find out.