The city of Caulderon is the mythic flying city. Once a magnificent city on a cliff, it was saved from being lost to the sea by being lifted by alchemical means. It was filled with impossibly tall shining spires standing above golden domes. The sunlight striking it is said to blind those who come to invade the city. The people lived in this magnificent city in health, wealth, and safety. They rode Griffons and created all sorts of creature. Caulderon was known for its magic, its alchemy. In the old tongue, the word Caulder means alchemey, from the word Cauldron. It is from their alchemey that their great wealth and comfort is derieved.
Legends (and Elven History) states that the floating city would visit The Lands once every few years, blown by the winds. They would trade for things and sell their magikal goods. After a year or so, their cities would be be blown to other places. It has been over four hundred years since any credible source has seen the floating cities. It is the thing of legends.
Then why has one been seen over the Land?
The PCs accidently start a fire and are caught by the local law enforcement. Since it was accidental, the punishment for the PCs is to fight the fire. Providing they can put it out before it burns down the town, they will not face any further punishment.