Slaughter Swamp is a location on the outskirts of Gotham City.
While Hospital Brass was being cleared out to make room for more patients, two orderlies brought Butch Gilzean's comatose body to Slaughter Swamp and dumped it into it's waters. After they left, the biological waste containers from Indian Hill that were dumped into the swamp revived Gilzean in a zombie-like state while also regenerating his hand. Stumbling upon some campers, the amnesiac Butch attacked them when they took action towards him where some of them were knocked out or retreated. Taking the name Solomon Grundy from the rhyme song that was playing, he borrowed some clothes and made his way back to Gotham City. 
Months later, Oswald Cobblepot went to Slaughter Swamp and salvaged one of the Indian Hill barrels. He used it to sway Solomon Grundy to his side where he makes plans to find Hugo Strange to see if he can restore Solomon Grundy back to normal.
- "A Dark Knight: The Blade's Path"
- "A Dark Knight: Hog Day Afternoon" (mentioned)
- "A Dark Knight: Stop Hitting Yourself" (mentioned)
- "A Dark Knight: Pieces of a Broken Mirror" (mentioned)
- "A Dark Knight: Mandatory Brunch Meeting" (mentioned)
- Slaughter Swamp is a location within the DC Universe continuity, first appearing in All-American Comics #61 (October, 1944). It is commonly used for the origin of Solomon Grundy, as Cyrus Gold's body is dumped there after being murdered and he later comes back from the dead decades later as a zombie.