Blackout

Blackout is a multiplayer map featured in Halo 3 and is a remake of the classic Halo 2 map, Lockout. It is featured as one of the three maps in the Legendary Map Pack that became available on April 15th, 2008.

Rather than a Forerunner facility, like its predecessor, this map takes place in the Antarctic on Weather Station z/41. The layout is almost identical to that of Lockout, but features more grenades and now includes equipment. Most of the jumps, even the crazy ones from Halo 2, are still there. However a number of things have been modified or removed such as one area which was altered to make it more difficult to lock down part of the map.

Blackout's code name was Moonlight Sonata during its development due to the levels dark nighttime sky. It replaces Purple Reign in the Halo 3 Legendary Map Pack. Purple Reign will be included in a later map pack. Such changes as the blue lift to fit the new environment has been turned into a red air vent.

Bungie almost didn't make the map, because they already had Guardian, but with fans still asking for one, they went ahead and made it.

Geometry and Forge
In the most recent ViDoc, multiple forge items from Lockout were revealed. They include stair cases, man-cannons, standard dooring to block doorways, shield doors, and newly edited shipping crates which stay once they placed on. A full tour of this map can be viewed here. According to 1up's update, Blackout contains a basket ball hoop and the BR tower is now featured with windows compared to being fully opened.

Trivia

 * Blackout's codename was "Moonlight Sonata" (an allusion to one of Beethoven's works)
 * The Aurora Australis is visible in this map.
 * The layout of the map is a direct remake of Lockout from Halo 2 (albeit with a Human theme instead of Forerunner). The only other direct remake in Halo 3 is Last Resort which is a remake of Zanzibar.
 * Bungie claims that the model for Blackout was rebuilt because the original model of Lockout was too messy to work with.
 * The only weapon spawn point differences is that the spawn points where the Needlers used to be have been replaced by Brute Spikers.
 * The old death defying jumps for Halo 2's Lockout can still be accomplished.
 * Blackout has more Plasma Grenades than Fragmentation Grenades. It is the only map in Halo 3 for which this is the case.
 * There is a basketball hoop located in the Barracks building in Right corner.
 * It is so far the only Halo 3 map to take place during the night.
 * This map's background is currently Bungie's wallpaper for their website. However this is not the actual in game render. You can tell this because the moon isn't high enough in the sky (when compared with the moon in game) and the Aurora isn't on the same side of the map as the moon.
 * The Laboratory building contains ice core samples, suggesting that the workers at the platform conducts research on ice besides weather.
 * The map is slightly larger than Lockout in some areas, the Battle Rifle tower is larger, the Barracks are smaller, and the Platform next to the Sniper tower is larger.
 * It may be a coincidence that Blackout was released on the same day that the HMS Titanic was destroyed and on the map there's a massive iceberg in the background along with the water below the map being scatted with ice.
 * Blackout is the most selected map in matchmaking in DLC Slayer with Ghost Town in 2nd and Avalanche in 3rd.
 * Upon falling off the platform, a splash can be seen after your character lands in the water. On other occasions, if your character lands in the water flat on his/her back or stomach he/she will land and slowly sink downward.
 * Players tend to camp at the bubble shield spawn point and are often seen throwing grenades down the ramp until an opponent is killed.