The Underground

"It's a hole! Oh, excuse me, a historic hole."

- Nick

"Aw man, this tour is bullshit."

- Coach

Underground is the second chapter in Left 4 Dead 2 ' s The Passing campaign. The Survivors exit the safe room and head through streets and a bar that contains a jukebox until they reach the historic "under the river tour". The second phase takes you through a sewer that has two gates that when opened activate a alarm. The Survivors must run to the safe room while being slowed down by water and hordes of Infected.

Campaign
In the beginning of this chapter there is a high chance that a Fallen Survivor will spawn. Take to time to carefully turn off your flashlight and snipe it, this will give you some supplies right from the start. A lot of foot lockers and one M60 will always spawn. There is also something that may surprise you on your way: when you reach a fence covering a road you will hear an oncoming truck. When you put the game in slow motion you will see the Midnight Riders' tour bus.

There are at least three separate points of no return within the last leg of the level: One being the stairs leading down into the sewers and the other two being both of the starts in the marathon gauntlet. Use extreme caution when dropping down from each of these points.

There are several parts in this chapter that the Infected can really do some damage and most likely cause your team to die, especially Tanks, Smokers, and Jockeys.
 * The first one is the stairs right outside the safe room. A Fallen Survivor will almost always spawn here so try to take him out with a Melee Weapon or M60 or alternatively, push him into the wall and work him down before venturing further, because especially in Versus, there might be a Boomer or Spitter camping in one the alleys next to the stairs, so try to have a Survivor on point to check it out. If they get puked on, have them head back up to the safe room, and have the other non bile covered players cover them.
 * Next up is the Construction Site. Most likely there will be either a Horde, a Witch, or other Special Infected that could easily pin down a Survivor, and if the team isn't fast enough they could get incapacitated or killed, because the others might be already in the Pool Hall. The area is also a Swamp-like terrain, which will slow all Survivors down who don't have Adrenaline.
 * Speaking of the Pool Hall, there will be a jukebox which will get you an achievement but also cause a panic event. In that case, if you have been playing through the whole campaign, there should be tier two guns and possibly a foot locker, so camp in a corner and wait it out. There very well may be a Tank, so a very good tactic is have the healthiest player attack the Tank first, and lead to one of the pool tables, and have it chase you around the pool table while the others open fire and light it with molotovs or cover them with bile bombs.
 * Next one is the plank outside of the apartments that leads you to the streets. This an obvious spot for Smokers and Jockeys to take out one of your team, and an exploding Boomer could take out a whole team. Just don't drift far ahead, act quick if someone else is pinned, and you'll be fine.
 * After that, the streets will sometimes spawn a Tank. It's an open area, so it shouldn't be to difficult. There might be gas cans in the Jazz Club so have one person get those and light it up.
 * The Under the River Tour is a Jockey's paradise. There are many dark rooms that the Jockey can lead a Survivor to very quickly, so try to have all four players be almost right next to each other so a Jockey can't surprise attack a stray Survivor from behind.
 * After you drop down the stairs, if a Tank hasn't spawned yet, it will here. Just try to confuse the Tank by firing from all directions and moving around. If you try to go a certain way, it will most likely catch up to you, being it's a Swamp terrain as well. If the Tank comes near, dodge his rocks or just hold out until it dies, because the others should be focusing fire on him.
 * The gauntlet should be a breeze, have someone with an Auto Shotgun or M60 go first, to clear out a path way. If this doesn't happen, the Common Infected will endlessly swarm until you make it to the safe room, so have one person stray forward while the others are behind him distracting, as a secondary option.

The Survivors
Tips In the Pool Hall, be sure to check those windows and clear out some of the Infected ambling around the Construction Site. And, when you and your team move through the Site, be sure to climb on top of the parked construction machine so that you can get out of the movement-hindering water and snipe some of the Infected in the Bar.
 * Stick Together! If you try and rush off, you'll be easily wiped out by any of the Special Infected.
 * Keep your eyes open, and be sure to check your corners. You never know if a Charger might come roaring down on you the second your team rushes around blindly, so peek your head around the corner to make sure they aren't waiting for you.
 * Watch the rooftops. A common problem of Special Infected is their tendency to prowl the rooftops and then try to get the drop on you. If you watch those roofs, you'll most likely be able to snipe more than a few Smokers waiting to snatch you.
 * Turn your speakers up. Sometimes, your team-mates won't hear the Special Infected themselves, so if you report them to the bark of a Charger or the growl of a Hunter it can keep them on the lookout and not have them surprised.

Through the Bar, you'll have to ascend the stairs and then cross to the adjacent building using a fire escape and a narrow plank. Here is where the Special Infected can easily trip you up the most. Keep a sharp eye on the alley, on the windows of the building, and behind you so that no Jockeys can get the jump on you and pull you over the edge. If one of you fall off the plank and hang from the edge, that could give the Infected the opportunity they need to take out the rest of your team.

In the large underground chambers, be sure to keep your eyes at the pillars. Smokers are often hanging around there waiting to drag your friends into the dark. For the Crescendo Event, try to make sure everyone has adrenaline, so that you can take the shots and then sprint down. Be careful on the stairs, as that is a prime opportunity for Chargers to get in their hits.

The Infected
Tips Try to deal as much damage as you can before the Survivors make it through the bar and into the sewers. The reason for this is because if they are moving slowly, you will be able to pick them off in the massive underground chambers easily. Have Smokers just behind the large stone pillars so that he can just barely see the Survivors, and have Hunters at the ready. If you are a Boomer, simply rush ahead and wait at the tunnels as the chambers are much too large for you to be effective.
 * Lone Wolves are always easy fodder.
 * This map is mostly close-quarters, though about partway through it opens up to massive, expansive areas.
 * Partway through, the Survivors must cross a small plank from one building to another- if you can find a way to knock them off, then you'll have an easy way of hindering their progress.
 * Be sure to camp those weapon and health kit locations! Whenever Survivors see good weapons, they are always going to go get them, giving a perfect opportunity for a hiding Boomer or Spitter to get in some damage.

When your Smokers snatch the first Survivor and pull him back, be sure to have a Hunter or Charger hit the Survivor or Survivors that go to save them. If you can't wipe the Survivors out in the chambers, have a Charger waiting at the top of the steps to bowl all of them down when they get there. If that is pulled off correctly, it should damage them greatly and allow the rest of the Infected Team to knock them out.

A great strategy to do is have a Charger waiting just below the gate that activates the Crescendo Event. From there, if you wait for the Survivors to drop in front of you, you can charge one of them and take them a long ways across the chamber. That should get you at least two or three slams in, maybe enough to incapacitate.

Survival
There is a glitch in Survival whereas the player can reach an invisible ladder leading to a balcony.

However, the Infected cannot reach the Survivors, and the only danger are Smokers and Spitters, but these can be avoided by staying off of the railings and crouching in the center of the balcony.

To get to this balcony, the player must travel towards the underground tunnel area. This will be blocked-off in Survival. There should be a neon-light sign hanging above the closed-off entrance to the tunnel; next to this sign is the Jesus-room balcony. The player should travel to the right of this balcony, next to the ivy. The player party should approach the ivy from the parallel brick wall. This will take a few attempts, but the players should discover an invisible ladder that leads to the balcony.

Once you figure out the ladder and become comfortable with climbing it, send someone to start the radio. The rest of the team should cover them as they return.

As long as the player party takes out any Smokers or Spitters, they will be untouchable on this balcony.Unless Tanks are to throw slab of concrete. Very rarely a Hunter is able to pounce and land on the balcony.

If you choose to play this without a glitch, a tactic is to stay at the spawn area and close the doors. Have two people guard the entrance to the streets, two people guard the entrance to the construction site. If you do this, by the time the Tank arrives you should be at full or almost full health. then have someone head to the streets with a gas can and every one else follow. If it doesn't spawn on the streets, have two guard the entrance it will come in and place the gas can there. Shoot the gas can, light the Tank up, and you shouldn't have taken damage. If you follow this you should get a bronze medal at least. It's recommended to have at least two people doing this.

Easter Eggs

 * Most of the graffiti in the bar are references to other zombie games and movies, such as:
 * Dead Rising, "Otis, out of film. No helicopters. Zombies too fast. Not going to make it.-Frank West"
 * Plants vs. Zombies, "Need an M60? Come see me! - Crazy Dave"
 * 28 Days Later, "Repent! The end is extremely fucking nigh"
 * Shaun of the Dead, "Ed is king of the zombies"
 * Dawn of the Dead (1978), "Roger, went to the mall, Francine"
 * Dawn of the Dead (2004) "Went to save my dog. If not back in 15 minutes, drop everything and come save me.-Nicole"


 * [|The Venture Bros], "Hey MOL. Meet me in town we'll have some fun! -Brock"
 * There is also a reference to the infamous Chicago Ted in the bathroom where it states "NO TOILET IS SAFE FROM POOPING KEVIN".
 * Sometimes you can see the Midnight Riders tour bus leaving. Which could mean that the band members are in it, probably heading to Whispering Oaks for the next concert on their list, although it is possible other Survivors are just using it as a mode of transportation. However, in Dark Carnival's finale, they are not present. Graffiti states they got evacuated by helicopter.
 * In the jazz club just before the gauntlet, there is a small stage set up with Midnight Riders equipment on the stage.
 * There is a poster in a bus stop advertising Mercy Hospital blood transfusions.
 * There is an easter egg in this level, a suitcase full of pistols and money. The lyrics from the song "One Bad Man" by the Midnight Riders is referenced by this. All of the Survivors comment on this. Coach sings that part of the song, Nick says he likes how this guy packs, and Ellis will say "Hell yeah!", and Rochelle will jokingly ask if it's Nick's suitcase.
 * Rochelle might mention that the tour is worse than the Seattle Underground Tour, in reference to Valve being near Seattle.
 * Nick curses Jimmy Gibbs' name many times in this map, often calling him "Jimmy Goddamn Gibbs".
 * If you look closely at the back of one of the biker Common Infected, you can see that it says "zombie".