Nightmare (titled zps_nightmare in the game files) is a medium-large sized map set in New York City during a thunderstorm. There are five main locations on the map: the hotel, the street, the subway, the rooftops, and the back alley. Unlike most urban maps, a moderate amount of the weapons and items spawn outside of the buildings in this map. It has a fair amount of indoor and outdoor action with many alternate paths the player can take to get to key locations, leaving no place on this map easy to camp.
- Kill the survivors
- Avoid cluttered areas initially until you find decent weapons suitable for combatting zombies indoors.
- Be cautious when turning corners indoors, as zombies usually hide out of sight for easy kills on humans.
- Note where the exits are so you can quickly get to one if you find yourself overrun.
- If you are panicking or retreating in the hotel, stick to the walls so you can cut corners quickly when on the run, breaking the zombies' line of sight with you.
- Ambush the survivors in tight spaces.
- Get to weapon spawns before the survivors do and wait for them to walk by, then attack.
- On this map especially, sneaking up behind a survivor is preferred, as there are many narrow hallways that prevent the zombie players from dodging attacks efficiently should they be spotted by survivors.
- If one were to wait in the subway tunnel long enough, the sound of a Combine Siren from Half-Life 2 can be heard in the depths of the tunnel.
- This is one of several maps to have a dead Eugene ragdoll placed in it.
- Walking into the room with the holding cells for the first time will trigger on a non-lethal explosion for unknown reasons.
- In the holding cell room, the cell on the right has an old radio on the floor. It infinitely loops an ambiant noise from the Citadel from same game of a Stalker yelling in pain and groaning rather ominously in reverse.
- In the first room on the right after opening the double doors to the hotel, there is a switch on the wall. Pressing the switch will trigger the sound of Barney Calhoun, once again from HL2, laughing. This can only be done once per round.
- This was the first map seen in the Zombie Panic: Source trailer.
- This map was made by Knights, the same mapper who made Police Station, Haunted, and Deadend.