Anywhere but FLORIDA. Please. Be a decent god...
'lol jk im not that mean'
Phew, that would've been a close one! 
- --Filthy Frank and Chin-Chin on Salamander Man being taken there.
Jacksonville, Florida takes the cake for the worst city and dimension ever, even worse than Hell, Fake Africa, and カンチョー combined. This city showed that even Chin-Chin has a little bit of a heart in his black dark body for his victims, as proven with Salamander Man.
Naming
It is unknown why this city was called Jacksonville, Florida, as most of the craziness that actually happens in Florida in real life mostly happen in the Miami, Orlando and Tampa metros, aswell as Lakeville and Gainesville. However, the naming was mostly due to the fact that in real life, Jacksonville is the most populated city in the state.
The kidnapping of Salamander Man
When Chin-Chin took Salamander Man from Frank for not sacrificing chromosomes, Chin-Chin refused to take the great assflute player to Jacksonville, instead cursing him and keeping him hostage at the Rock Paper Scissors Arena, but this is possibly due to the fact that his enemies reside here, but that before that, they were his prisoners but then they have broken free as a result of not being a true god.
The Santa's Brother mystery
Santa's brother claimed that he shot a kid and an old man in the kneecaps in Jacksonville, Florida, but it is unclear, since he only said that this happened in Florida. When Frank uploaded a video called "I saw Santa Claus", he actually claimed that there was a strange guy dressed up as Santa Claus that actually shot him. It presumably means that Filthy Frank went previously into an adventure in Jacksonville but then was shot by Santa's brother. In another video, Frank claimed that he burned a kid in a wheelchair to create hot wheels. It presumably means that Frank burned the handicapped kid that Santa's Brother shot in the kneecaps afterwards.
It is possible that due to the fact that Frank was reported to be shot in Florida, Chin-Chin is haunting him since he appeared in "CHIN CHIN (A SERIOUS VIDEO)", but this is also possible that his trip was 6000 chromosomes between Chin-Chin's death and his first appearance to The Filthy Frank Show, but there is speculation that Frank did not startle the dark lord but much rather Santa's Brother.
The Unknown
It is unknown why this specific city in Florida is the worst city and dimension ever, but this is possible that "the nightmare" is a hoax that has been spread by Chin-Chin himself, as his prisoners, which are his most powerful enemies that Chin-Chin have sent there, might have bend together and control the dimension by themselves while the dark lord loses control, and none of the entities who have visited this place were seen affected by horrible things that are suspected to happen there, such as Frank and Santa's Brother. Due to this, this possibly makes Jacksonville one of the safest places in the omniverse but that Chin-Chin has to call it one of the worst places in the omniverse, and so his throne made out of child flesh was destroyed, and so he has to move his throne to Monoxide 12.
The Safari Man mystery
It is unknown if Safari Man owns illegally a daycare in Jacksonville, as he was presumably heard raping his sister's boyfriend inside of his house, which he turned it into his own personal daycare, as no trial has ever been heard since, although this was during an episode of Japanese 101.
Other information
It is said that Evil Dade and Negative Chin Chin reside in this dimension. It is also said that this is where Chin-Chin has created a demonic soap bottle and put it for sale in the market, but that this attempt to take over the omniverse has failed due to the lack of powers given to it, as it shortly lived as Pink Guy killed it in one single throw of trash paper.