Wow, this looks so totally... different. New HUD, new textures, new sky, new bobs, new fighters. You have two fists now! The Bobs talk, and teleport! You can hear the wind! One slightly major difference I can think of between this level and the version in the preview is that the level used to take place during the day. Perhaps this change was made so that Bungie could remove the night landscape from the preview and thus decrease its size. Although it was still a shock back then to discover that the preview was somewhat larger than Marathon 1 itself. Down the corridor is another of the major differences between Marathon versions: The new terminals have formatted text and pictures! Very interesting possibilities here...
The level is linear but nicely connected, with two major areas and paths through the level. It makes good use of Marathon 2's new abilities; in general Marathon 2's maps are far more complex and detailed than M1's; of course this is only to be expected in a sequel and they still usually don't approach the sheer scale of Marathon Infinity or later third-party efforts. In fact, I was somewhat disappointed that so little of M2 was spent on spaceships in general. We don't even see the Marathon ever again!
Moving on into the second outdoor area, we are introduced to even more of Marathon 2's surprises: Teleporting monsters and ammo. Can't scope out rooms before you enter them any more, something could jump out at any time. The Bobs are much more useful than before, but that's not saying much, especially if you are playing on TC :P Double back to the second chip insertion point to save and recharge, also take a peek at the terminal, which features a screenshot of a texture that does not appear in M2 (but might have been in the preview, I don't remember).
This level has a good supply of optional areas (rather like Arrival, but unlike Ne Cede Malis). Off the outdoor area is a pair of large rooms containing the M-75, some dancing lights, and the main entrance to the secret area. This room is also the destination of a small path that led from the water-trough room earlier in the level (which also had a second entrance to the secret, behind one of the central walls). Definitely pick up the M-75 even if you're in a hurry, it makes your job much easier on the next few levels.
The big secret on this level is quite a treat. It gives you, among other things: A peek at the (retextured) water tank visible in the terminal earlier and which plays a part in one of the Windows version's secrets, the almighty WSTE-M Combat Shotgun and a lot more ammo for it than you think (try walking past the alcove where it's found several times), a ton of Fighters to kill, and a large watery room that shows off Marathon 2's liquid abilities and gives you several routes back to the beginning of the level. All in all a nice start to the game.
