Half the city flies and it's all connected by gates; a city of wizards and sorcerors and their works. The Archmage dwells here in a flying fortress, directing his massive defense grid.
During the fifth age, Bungo Hillshire killed one of the most skilled and subtle Illithid infiltrators of the surface world as it was returning to the Underdark, it's head full of priceless knowledge that would never reach the Elder Brains. Bungo put its head in a jar. Halflings sing a song today about Bungo, though it is a variant of 99 bottles of beer on the wall, where it's 99 Illithid brains on the wall. And it counts up. In Horizon (99 Jars), there is a bar with 99 Illithid brains on the wall, but probably none of them are the one the Illithids want and most of them are probably fake.
Grape on the Vine allegedly conveys the 'authentic Horizon Dock Dive Bar Experience'. This is possibly the fakest place in the Empire, from staged brawls to prostitutes who spend over a year training to fake being cheap floozies. The wealthy and novice wizards come here to see what it's like and it's all basically a show. An expensive show.
Horizon has many bars, inns, and taverns which only cater to locals and this is one of them, only the secret got out. You go to Luigi's House of Plumbing and ask about Fire Turtles and you get let into the secret bar. Locals have given up on keeping out outsiders and so it's full of people from elsewhere now, while locals quietly go somewhere else. Ironically, this has made it a major hangout for adventurers in a district that normally has none.
This is a popular but expensive restaurant in one of the flying districts; it caters to a wealthy clientele and adventurers who don't have a bodyguard license will have to check armor and swords at the door. If you can afford it, though, the finest Glitterhaegen cuisine is yours for a reasonable price (if you're wealthy or an adventurer). Security is pretty strong, and anyone who causes trouble will soon be swarmed by Horizon forces.
This is an inn on a flying island which is both in the air and underwater at the same time, somehow. The outside walls are glass; from the inside, you can see into the sea and if you have enough money, get an undersea tour. (From the outside, the outside walls show ever changing images of the sea.) There is a nightly music show, and a few nights a year, a drama or comedy is performed in the restaurant, which of course, focuses on sea food.
Velvet Jones, a retired sorceror, founded this school to help people train in sorcery and is rumored to possess secret methods to awaken people's abilities. He's also rumored to be running a brothel staffed by some of his students. Well, it's not so much rumored as pretty well known but public officials pretend not to know. Velvet is a Fortunan, with wild purple hair and green skin. Despite his pimping, there's plenty of evidence his methods often work. The Imperial College of the Arcane hates him but he has an Imperial charter.
In the Sixth Age, the demented Emperor Leto II was obssessed with somehow becoming a purple worm. He acquired a huge library of information about shapeshifting. On his death (eaten by purple worm babies in some insane ritual), his library was passed to the Archmage, who had this place built. Any lore discovered about shapeshifting is added to it; this huge obsidian rectangle is bigger on the inside than the outside and run by competent, helpful librarians, though there are rumors that anyone who asks about purple worms is guided to information which will kill them. Probably only a rumor.
This is a dive bar for sailors, prostitutes, and the down-on-their-luck. And pirates. It's down in the subcity area of Horizon. You'd never guess you were in Horizon, though; there is no magic, just mundane food. They don't serve real rats, but they have a strange dish where they take a big meaty tuna and carve it into fake rats, covered with shredded cabbage. This comes with an onion and potato soup. Most days, there is a brawl, if that's what you want. Every so often, stupid tourists come here and die and it gets shut down but that never lasts long. The staff claims the Archmage comes once a month in disguise to get rat soup but this is almost certainly a lie.