In Modern Combat 3 there are 8 different, diverse maps for multiplayer usage. They are a huge upgrade from it's predecessor as they have increased in size massively and are more layered ( in Modern Combat 2 the maps were very flat and would have extremely few if not no raises and/or drops in the terrain). These maps are:
The largest map. An open area with a few warehouses scattered around the map and a large warehouse up the back. This map is made off a segment of the mission "Surgical Strikes" from the Campaign mode. The idea for this map is to stay around the edges of the map, never run through the middle, this generally results in a death.
The smallest map. A dark map made up of two landmasses on either side with a bridge connecting the two. A good tactic on this map for Capture the Flag is to crouch and slowly creep down the smaller part of the bridge on either sides, as many people do not know they are there, and while the battle is going on in the centre bridge you can stealthily creep into the enemy base and steal the flag. This map is based on the mission "Cold-Blooded" in campaign mode.
A boxed in nuclear missile launch pad. This map is a cramped maze which is difficult to navigate at first. This map is based on the final mission in the Campaign and that is why it is called Countdown. A good tactic on this map is to hoard kills until you can deploy a turret and then deploy it in the enemy spawn, in a shadow (so it isn't destroyed) at one end of a small corridor or next to a capture point e.g. zone in zone control, flag in capture the flag, hacking device in destruction etc...
A varied map of medium-large size containing farmland but also suburban houses and buildings resembling schools. This map has lots of camping spots on the outside of the urban courtyard area so try not to walk through it if you can. Also this map is very good for using airstrikes on, for me its a 80% chance it will get me a kill, compared to 15% on Scramble.
An extremely poor village in Pakistan. This map is medium-small size and revolves in a circle. Don't stay on the lower bridge in the centre for too long as there are often campers that shoot through a gap in a cliff from the upper bridge. It is a well layered map and has lot's of props to be played around with for great replayability value forming cover for longer, more adrenaline packed firefights. Be careful on lower generation devices for this map has very laggy sections to it i.e the area around point "A" during a Zone Control match.
The second largest map, arguably the largest. This map is based on the first mission in the Campaign; Operation Blockbuster. It is set in the rooftop of NSA (National Security Agency) building in Los Angeles. It appears to be Medium sized at first yet layers enlarge the map making it a great map for replayability as you will keep discovering new areas you didnt know existed. A good tactic o this map is to place a turret at the end of the long corridor ( Point C on Zone Control ) by the soda machine.
A map that was added in a large update on June 7,2012. It was also in Modern Combat 2: Black Pegasus. Gameloft said it was in popular demand so they added it.
An all new map added in a large update on June 7,2012. It is an all new map that is exclusive to Modern Combat 3; Fallen Nation. The location is in the middle of a jungle where a showdown is happening.