Snowbound

Snowbound is a medium sized multiplayer map in Halo 3. From Bungie Q&A on a weekly update, they hinted that it may take place on a Forerunner planet near Earth space, though it is currently occupied and being excavated by the Covenant.

Layout
Snowbound is a medium sized, semi-symmetrical map set in a snowy Forerunner Construct with two large Covenant bases at either end, connected by an underground tunnel network. Several rock outcroppings are found around the perimeter of the map, as well as other Covenant and Forerunner constructions. One unique feature of this map is the infamous shield doors. Similar to those found on Epitaph, these doors stop all weapons and explosions, but let players pass through; although Spike Grenades can stick to the shield itself. Due to the structure of the map, fighting often takes place in or around these shield doors, and players above ground are often picked off by Sniper fire. The most unique part of this level however, is the level boundaries; here Automatic Turrets, shoot any players venturing outside the maps boundaries.

Low Base
Often referred to by players as "BR Spawn" due to the two Battle Rifles present at the back of this base, Low Base is nearly identical to High Base in shape and structure. On top of the base players can find a Needler and a Plasma Pistol, as well as Plasma Grenades. Outside, players can also find a Carbine and a Brute Spiker, in addition to a Mauler (to the left of the base) and Active Camouflage (to the right of the base). One of the maps power weapons; a Spartan Laser, spawns inside low base, as well as a Bubble Shield, and a pair of Spikers. Players can also travel to the Ice Cave via ice tunnels connected to the base by a small shield door.

High Base
Directly opposite and nearly identical to Low Base, High Base offers players a different weapon set than what is found at Low Base. High Base is commonly referred to as "Sniper Spawn" or "Carbine Base" due to the Carbine and Beam Rifle which spawn in this location. A Needler and Plasma Pistol, as well as Plasma Grenades can also be found on top of the base. Behind the base, players can find a Battle Rifle or a Plasma Rifle around the rock terrain. Additionally, outside, players can find a Mauler to the left of the base, and an Overshield powerup to the right. The base interior houses the other power weapon of the map; the Beam Rifle, along with a pair of Plasma Rifles as well as a Power Drainer. Note that the turrets can be blocked in forge.

Upper Map
The upper portion of the map is home to many predominant features and access ways, and is also a Sniper's paradise. A single Ghost is present on the far side of the map nicknamed "Underpass" or "Ghost Spawn", and is located in between both bases. In the center of the map, players have access to the maps lower levels via the Ice Cave Tunnel. A common tactic for players is to randomly toss grenades into the map's lower levels from this area; utilizing the underground corridors and tight spaces to trap players in the explosions. On the opposite side of the Ghost, players have another access point to the lower level through the Ice Cave's main entrance. Snipers often take the Beam Rifle to the upper levels and camp by the Rock Slide or just on the fringes of the map (carefully placed where they turrets will not fire on them) and pick players off who are brave enough to travel above ground.

Ice Cave
Predominantly known as the "Shotgun Spawn," due to the only Shotgun on this map, heavy fighting occurs in this cold and icy cave. Though this area is a deathtrap, players often find themselves at odds with their enemies as they travel from one base to another. The shield door on the main entrance is often used to taunt players inside or outside while lobbing grenades though the door, and quickly backing up. Above the Ice Cave, players can find a Brute Shot on top of the Forerunner construct, as well as a Spiker to one side and a Mauler to the other. Players have several points of entrance and exit, but the tight quarters of this cave make maneuvering quite difficult. An often seen tactic on this map is to hide on the other side of a shield door with the Shotgun or Mauler, and kill players as they pass through. Also if you throw a grenade on the other side of the barrier it will still set off the power cores.

Areas

 * 1) Low Base - Bubble Shield found here
 * 2) High Base - Power Drain found here
 * 3) Low Base Batteries
 * 4) High Base Batteries
 * 5) Rock Side
 * 6) Tundra Side
 * 7) Ice Cave Entrance
 * 8) Ice Cave
 * 9) Ice Cave Tunnel
 * 10) Ice Tunnel
 * 11) Underpass
 * 12) Far Rocks

Glitch
One of the most interesting things about Snowbound is it's unique glitch with the Auto-aim Turrets and Shield Doors. Basically, load the Forge and drop four trip mines near an Auto-aim Turret and set them to instant respawn, stand on said pile then just throw trip mines onto the Turret. After about two minutes of constantly throwing trip mines the Turret will disappear. Now, destroy the trip mines with a grenade and walk away for a minute. The Turret will respawn but not shoot at you. In fact, none of the turrets will fire at you. The shield doors will also disappear allowing vehicles and projectiles through. This is also done in Sandtrap to disable the mines.

A film clip created by TheSkunkrocker was uploaded showing how to make the turrets disappear.

Trivia

 * This was the first Halo 3 Multiplayer level ever shown to the public.
 * Snowbound is also the name of a 1994 movie, starring Neil Patrick Harris and Kelli Williams.
 * Beneath the Bungie logo in the screenshot of the battle, you can make out the term Out of Ammo written in the sky. Beneath it is Press (Y) to...
 * If you get out of the map boundaries then the turrets will shoot and kill you.
 * When you venture outside the boundaries a siren wails as a warning to go back before the turrets kill you.
 * In the Beta you could use a bubble shield to defend yourself from the stationary AI turrets, allowing you to travel further out of the map than usual. This has been fixed in the final version of the game though.
 * A tactic introduced after the Beta is for the leader to rush out with the oddball and be killed by the turrets, leaving the ball unattainable.
 * Like Sandtrap players may leave footprints in the snow (which could be tracked) for a few seconds before fading away. This is helpful when opponents are in active camo.
 * According to several players who have photographic evidence, there is a secret room somewhere below Snowbound, this is done in forge by overloading the map so the energy doors disappear, then drive a mongoose in the main room of the Ice Cave, create some crates on one of the walls and wedge yourself between them and the wall on the mongoose, and get out, this should send you through the wall, and under the level.
 * In the sky, you can see the 'northern lights' (a.k.a aurora), which are common in colder climates.
 * Even if Invulnerable, the Guardian boundary turrets will still kill you.
 * In the sky, the visible planet has a Marathon symbol on it, it could possibly be the Legendary Planet.
 * Below one of the bases the "Blue Room" can be found. In order to get there you need to get a respawn points under the base and kill yourself.