Official Halo 3 Team

The Halo 3 Maps including skulls.

Foundry is the ultimate Forge map. Players can edit every single object in this voluminous industrial warehouse, placing stairways, walls, bridges, and tunnels to create an entirely new play space and build almost any kind of map imaginable. It's core set-up is a symmetrical, small map, that funnels players to the center for combat and the perimeter for Sniper Rifles. 

The symmetrical valley of Standoff, with its entrenched bases and fields of boulders is ideal for mid-sized objective and Slayer game types. Standoff is a mid-sized map set in a symmetrical valley with foliage, orange colored boulders and bases entrenched on each end. Widely billed as the spiritual successor to Blood Gulch and Coagulation, Standoff is nonetheless dissimilar in many ways, being smaller in surface area, with larger, more labyrinthine bases. Standoff is best suited for mid-size symmetrical objective games.  

A large, symmetrical map with vast, labyrinthine passages. Rat's Nest bring something completely new to the multiplayer experience: an indoor vehicle paradise. Strongly influenced by the Campaign mode (Based off of the Crow's Nest Level), this map is ideal for big team battles. There's a whole mess of vehicles at your disposal to drive around the "circuit" -- a roadway loop running around the outside of this battle-damaged human holdout -- and a variety of hallways and walkways for players who prefer their combat tunes in the key of infantry.

The spiritual successor to Halo: Combat Evolved's large snowy vehicular map Sidewinder, Avalanche is the Halo Trilogy's current largest multiplayer map ever made.

All Human vehicles on this map are snow-camouflaged, and two vehicles, the Hornet and the Scorpion tank, are now available on this map in Matchmaking. However, the Hornet, which was a Transport Hornet, was "toned down" for Matchmaking due to balance issues. Avalanche was codenamed Cottonball.

The remake of one of the most popular and beloved Halo 2 maps, Lockout, Blackout was designed with a human theme layout unlike its predecessor Lockout, which had a Forerunner theme instead. However, they were both based in cold climates.

Blackout's setting is an abandoned drill platform in the Arctic, and has spectacular views of icy oceans and glacial formations. Blackout has a few spawn point changes that differ from Lockout. Blackout was codenamed Moonlight Sonata.

An entirely new map as announced by Bungie, Ghost Town bears a slight resemblance to the Halo 2 map, Turf. The map also may remind some players of a map of another popular FPS game, Counterstrike, due to its human-themed layout. Ghost Town was codenamed O.K. Corral.

Assembly was originally planned to be in the Heroic Map Pack, then in the Legendary Map Pack, but was replaced due to the fear that it wouldn't be finished on time. The map is set in a Covenant Scarab Factory. Some say it is similar to the two Halo 2 maps, Midship and Warlock. Assembly is fit for mid-sized Slayer and Team Slayer battles, and also supports objective gametypes, other gameplay details are indefinite. The map is symmetrical and only the second Covenant map designed for Halo 3 to date. If you look up, you can see a Covenant Scarab being "assembled" directly above you.

Orbital is set on the Quito Space Tether, a UNSC space elevator. It is the first map in Halo 3 (Campaign or Multi-player) to be set in outer space. Orbital is described as having two main U-shaped corridors overlapping each other and having some interesting switches that grant access to certain areas of the map. The first public image of Orbital was released on Bungie.net in late December.

andbox is a tiered medium-large sized map, and is a crossover between the desert landscape of Sandtrap and the Forge flexibility of Foundry. Bungie stated that Sandbox will be "the ultimate Forge map". Many new Forge objects are added to give players more options to make their own custom-created maps including, but not limited to, a golf club called the 7 wood, a Golf Ball, and a tin cup (golf hole). The map has a tiered nature. It is split into the "Sky Bubble", the ground, and the "Crypt." The Sky Bubble was designed so that Forge users could recreate maps akin to Guardian and Ascension since there is a grid only visible in Forge that will act as a death barrier, while the Crypt was added to create fully-enclosed arena maps using Grifball and similar gametypes. The ground was designed for vehicular maps more in the style of its larger brethren, Sandtrap. Every vehicle, weapon, and piece of equipment in Forge can be placed in the map.

"Longshore lacks the commercial ships that once made it a lucrative port for Old Mombasa, but it still bustles with activity. Designed for large scale combat and well suited for smaller affairs, Longshore’s multitude of industrial buildings, elevated walks, and open inlets conspire to create a complex battleground tailored for multiple combat scenarios." —Bungie

Heretic is a Halo 3 DLC map that can be obtained by buying the Halo 3: ODST game disc, available on September 22nd, 2009. Heretic is officially a remake of the popular Halo 2 map, Midship, this was confirmed by Urk in the 6/05/09 weekly update on Bungie.net.

Citadel is an upcoming Halo 3 map that will be shipped on September 22nd, 2009 with Halo 3: ODST. The Shotgun Spree achievement is attainable on this map. It is possible that this map is located in a Forerunner Citadel, similar to the one seen on The Covenant.

Bungie's Description: Citadel may be a long abandoned Forerunner stronghold, but its small, symmetrical confines are far from secure. Two opposing bases offer little safety for players looking for solace. Instead, Citadel forces small squads to stay in constant communication, keep their heads on a swivel, and be prepared to adjust combat tactics in close quarters.