Here is a pdf of my game notes for the flying prison of Highrock; it's written for 13th Age because that's what I've been playing for the past few weeks but the notes are light on mechanics and should be easy to convert to other game systems. In my game the player-characters went there to break out the notorious pirate Captain Morgan -- oh dear -- so that she could help them find a mysterious island to the east, where it was rumoured that a great treasure was hidden.
Through his connection to the Prince of Shadows Sartheen the Red knew that one of the wizard-judges of the city of Horizon was involved in some dubious activity involving an orphanage run by vampires -- that's player-driven storytelling in action! -- and so the party blackmailed said wizard into giving them the amulet they required to access the floating island and bypass the guards upon it.
They didn't explore much of the complex, in part because 13th Age doesn't reward exploration in the same way that older editions of D&D do, in part because they were focussed on the mission, and in part because they got beaten up by a squad of flying robots on the second level and wanted to get away as soon as they could. The latter was the result of robot sorcerer Ne-0n's attempt to interface with the island's local code -- he perceives reality as strings of data and can manipulate that data to a certain extent -- going a little wrong and alerting the guards instead of providing the location of Morgan's cell. Oops.
They also had some trouble with the Archmage's quarters, blundering into the fireball trap over and over again, but were rewarded with a fair bit of loot once they staggered past, all blackened and blasted like Warner Brothers cartoon characters; most of the players converted their relationship dice results into items at this point and as a result the Archmage's study held a plethora of magical stuff.
Morgan was freed and the party also let prisoner #666 -- the demon Zeddas -- free while binding him to Amras the elf wizard's service. Or so they think, anyway. They decided not to explore the third level, having been warned by the wizard-judge that death awaited them, and jumped on their waiting air taxi -- another relationship die traded in -- for a quick escape. With their navigator secured the player-characters were ready to go after their treasure, but first the Elf Queen had a job for them: to raid a nesting site used by the Three and destroy the unhatched eggs found there.