Underpass

Underpass is a large multiplayer map in Call of Duty: Modern Warfare 2.

Overview
Underpass takes place in the rain under the remains of a highway overpass. It's a great map for all types of weapons. It has narrow corners that make for unrivaled camping spots and wide curves that can hold devastating firefights. Players must be careful moving around, as it is a perfect map for hiding claymores and staging ambushes. In spectator mode, one can see the rest of the highway, and a large bridge.

Gameplay
Underpass is mostly a hit and run map, although there is almost constantly a sniper at either end of the map. Silencers work great on this map, since firing without a silencer will produce bright flashes at the tip of the barrel when firing, which will be heavily contrasted in the darkness of this map.

Controlling Killstreaks
Many air based killstreaks are little more than useless on this map, due to the tight and in-door nature of the map. Another downfall of killstreaks on this map is that Care Packages, Emergency Airdrops or Sentry Guns can get stuck on the overpass overhead quite easily. One of the safest places to call in Care Packages, Emergency Airdrops or Sentry Guns is in the parking lot on the far edge of the map, as people rarely venture over there.

The player should be aware of pinpoint airstrikes, it is easy to call them in on the highway rendering them totally useless.

Sniping
The Thermal Scope is highly effective on this map as it is very dark and player's images stand out as bright-white. Correspondingly, Cold Blooded is very effective at hiding from Thermal Scope users.

Warehouse B is a popular sniper ambush point, as a player can climb onto the short roof and go prone, as well as putting another member in the tall grass, giving them an easy opportunity to shred anyone coming up the side.

The small, red bricked, two story shack is popular for snipers and is perfect for getting one or two quick kills. It's open on all sides, there are two paths up. One is via the ladder on the side. The other is accessible by climbing the crates, which are located by the single tree near the bridge. A sniper with a claymore could easily camp out there for an extended period, as long as they maintain a watch over the exposed access point unguarded by the claymore.

It is almost impossible to spot a sniper who is hiding in the underbrush, especially if the player has Cold-Blooded, and has a camouflaged sniper rifle with a small sidearm or dark weapon. This map is great for playing dead in a Ghillie suit, because of the difficulty of identifying targets who are not moving at all.

Camping
The grass on this level is so tall, ambushing an enemy is fairly easy; even more so when Cold-Blooded and/or Ninja is used, claymores are also very useful in the long grass as one cannot see the red trip lasers. Heartbeat Sensors can be used to great effect in the in-door sections of the map.

It's possible to get on top of the large cluster of buildings in the center of the map. The player can get on the roof from climbing a pile of boxes, leaping from the burnt-out car, using the ladder within the shacks, or by jumping off the concrete piling with the ladder. Another camping spot is on a catwalk in the large warehouse with the storage tanks and long stairwell. Climb the tank next to the stairs on the upper floor and then climb onto the high beams. This is a popular spot for ambushing. The dark corner next to the stairs is a potential location to use controllable killstreaks or ambushes. You can also climb onto the handrail, crouch and drop onto a girder then hide under the sloping roof. The view is obscured a bit by the ironwork but it's a place not many will see.

The drainage channel can be used to good effect if the player lies prone in the water watching the crossing point on the western end of the channel, picking off unsuspecting enemies as they run across. You have to be quick but you cant be seen easily until they work out where the shots are coming from. It is also possible to get in the right position to snipe at the bridge and the container where some people climb and hide.

There is also a spot which can be found in the southern part of the map. There is an area at the southernmost end of the Shanty Town spot that is covered in wavy, rusted metal (Much like the roofs in Favela), that acts as the roof of a small room underneath. At the ground level of the map, this room is seen as a dark space with a square wall, a doorway, and two windows. Underneath it is an area of tall grass that is often used by campers. If the player walks out onto the edge of the roof and then crouches, they will fall through onto a ledge beneath. This may also happen without crouching if the player walks out far enough. From the ledge, players can hide in the room, which is very dark and not usually noticed by opponents, and snipe or shoot at enemies in the Storage Warehouse. This can be used without Ninja, because even if an opponent has a Heartbeat Sensor, they will merely think that the player is on the roof if they are on the ground, or vice-versa. Using a Tactical Insertion is not recommended, however, because the red glow is very obvious to the enemy.

Stealth
Stealth can be a major factor on this map. Using a silenced weapon with a Heartbeat Sensor can greatly help a player stay safe and not show up on UAV radar. Ghillie Suits also can help a player blend in when they are in the tall grass.

Trivia

 * A large number of players lose care packages by dropping the marker under the massive bridge.
 * In a small building in the middle of the map, there is a blue poster on the wall with the word "Roycewicz" and a phone number. Roycewicz is the private the player saves in Call of Duty 4: Modern Warfare in the mission "The Bog," and is a lead member of the Infinity Ward map design team.
 * There is a small train depot in this map with Kriegler train cars similar to the ones in the map Derail. This evidence shows that Underpass was likely to have been one of the maps to have the Train run through.
 * There is a poster up on many walls advertising a Infinity Ward "Rock Fest" underneath an African-American man with the name "Griggs," and has the Infinity Ward symbol on the top-right corner. This is a possible reference to Staff Sergeant Griggs from Call of Duty 4. Griggs is also the name of an Infinity Ward member.
 * There is a teddy bear in a warehouse on the catwalk.
 * There is a wall on the map that has "INFIDEL" written on it. On this wall there are also painted pictures of the AK-47 and Al-Asad.
 * There is a small banana plant on this map which can't be shot through even with FMJ equipped, similar to the ones in Favela.
 * Some of the shipping containers have IWCOD written on their doors, no doubt a reference to the Call of Duty franchise.
 * On the wooden walk on the bridge there is a take out box that has a smiley face and a message that says, "Have a nice day."
 * A ledge near Flag B can be accessed, although it is very difficult. This video (click here) shows the spot at 0:44.
 * There is a mattress on the ground near the sniping spot at Flag A on the side with no ramp, and the player can jump from the higher floor onto it and not get damaged, much like the mattresses in Afghan.
 * Outside the map is a crane reused from Highrise. With the use of mods it is possible to get on the crane.
 * The ladder to the lookout tower is very long and if climbing, the player can become extremely vulnerable to fire.
 * The player can place sentry guns inside the pillars supporting the bridge. (Patched)
 * A viral video that recently arose on YouTube was about an elderly lady opening a door when shooting the corners of the door with a certain number of bullets and then throwing a flashbang. The lady would then disappear for a few seconds, come back with a UMP .45 with a Red Dot Sight and Arctic camouflage, and kill the player. However, this has been disproved multiple times.
 * Outside of the map is a hidden river with boats from Karachi. These boats are frequently reused in certain maps.
 * This level is played in the movie Percy Jackson and The Lightning Thief.
 * This map and Storm are the only multiplayer levels in Call of Duty: Modern Warfare 2 to feature rain.
 * Even under the unfinished bridge, rain can still be seen falling through it.
 * There are some chickens found running in cages.
 * In some of the shady parts of the map, shiny looking guns, such as the .44 Magnum, may look like a dull grey.