Mercy Hospital

Mercy Hospital is where the Survivors are instructed to go to at the beginning of No Mercy. It was a hospital in the city of Fairfield. In the beginning of the campaign, the Survivors hear that a helicopter pilot is looking for Survivors, and that they should head to the roof of Mercy Hospital to get out of the city. Chapter 4 and Chapter 5 of the campaign reveal that all of Mercy's patients have been infected, and that the Survivors must fight through the hospital to get to the roof, and then defend their position on the roof until rescue has arrived.

Mercy Hospital is a large, thirty-floor hospital that has an elevator that leads from the 4th floor to the 28th floor, an isolation room (the possible location of the first victim of the infection), and a fully functional helipad on the roof. The 28th floor was still under construction before the outbreak (possibly a 28 Days Later reference), and was abandoned after it began. This is observed by the Survivors when they ascend the elevator, and travel through the maze of wooden frames to find a safe room.

Trivia
A complete list of hospitals with this name can be found here
 * From the levels The Subway and The Sewer, when looking at the hospital for a few minutes, a helicopter will fly onto the helipad of the hospital, land for a second, and fly back off. This is most likely the helicopter pilot trying to evacuate as many Survivors as possible.
 * Mercy Hospital seems to be a somewhat popular name for hospitals.
 * Mercy Hospital is the actual name of a cardiovascular hospital in Chicago, Illinois.
 * Portland, Maine also has a hospital named Mercy Hospital
 * Mercy Hospital is also a hospital formally located in Hamilton, Ohio, where many movies were filmed due to "that eerie feeling".
 * In the play Fences, there is yet another hospital named Mercy.
 * A hospital in the T.V. show Drake and Josh is also named Mercy Hospital
 * There is also a Mercy Hospital in Pittsburgh, Pennsylvania. Other references to Pennsylvania can be found, such as Allegheny Forest in the campaign Blood Harvest, and Pennsylvania license plates on various cars in the game. Incidentally, George Romero's Night of the Living Dead (and other movies by him) took place in Pittsburgh.
 * The Mercy Hospital elevator is summoned from the 4th floor, possibly a reference to the game itself, while it was waiting at the 28th floor, likely a reference to 28 Days Later.
 * While it looks complete from the outside, Mercy hospital's 28th floor is under construction. This is a possible mistake by the developers.
 * When looking at the hospital from any chapter where you are not inside (or on the roof) you can see the sign saying "Mercy". But if thrown off the building, the sign is not visible on any side.
 * Mercy Hospital can be seen in every chapter of No Mercy. With an exeption of The Hospital chapter when you don't see the outside of the hospital.