an overview of the map *Notice the tunnel connecting the two bases running under the main bridge*

the red base, identical to the blue base (below)

As you can probably tell, most of the effort went into forging the geometry around the bases and not the actual buildings themselves. Still, they each have 2 battle rifles, 1 mauler, 1 needler, and 1 regenerator, and various exits.
On one side of the map there is a pathway in the cliffs leading to an outcrop in the middle holding an active camo behind the waterfall.
Both bases can easily enter the cliffs through their respective gates. The blue gate is shown below leading up to the elevated path.
One of the things which I like most on this map are the sniper towers located to the right of each base (pictured below)
They each have a grav lift which respawns every 20 seconds to raise the player up to the platform.

Each tower has a sniper rifle in it which can be very effective if used properly but not too overpowering due to the two other routes (underground tunnel and cliff path) which are out of the sniper's field of sight. Personally, I don't like the roofs on them but they are essential as I found that you could escape the map by jumping off their sides. To get back down from the tower either shoot the grav lift and drop down or crouch while jumping to escape.

An overshield spawns underneath the bridge. Another way of reaching the opposition's side is also by walking over the tunnel rather than in it.
If you do fall of the bridge into the "void" there is an underground entrance
to your base (or the enemies if you're being particularly sneaky), which is also very near the tunnel exits.

Entrance to the tunnels. A mauler spawns at each base.
Well that's basically my map. I hope that you get a chance to play on it and can tell me how it plays because unfortunately only one of my friends has the mythic map pack and he's away on holiday, so I haven't yet played on my map but I would love to hear any feedback on that. In regards to the spawning problems; again I'm trying my hardest to fix it because it's very annoying to me. A few final notes: a brute shot spawns in the middle of the bridge and is probably the most "overpowering" weapon, please let me know if it ruins the gameplay so that I can change it; the tunnels have been merged to try and make it as smooth as possible but there are a few small bumps. I've worked quite hard on this map so I would really appreciate some constructive critisicm on how I could make it better. Thanks for taking the time to read my first post, it certainly won't be my last!
Incase you missed the link at the top, here is the link to "Crossing" on bungie again:
Download Map Here
P.S. I will try to get some action shots as soon as I have someone to play with + thank you Sorahn for Haloscreenshots.net it is AWESOME, made posting this a piece of cake :D