Castles in Clouds

A new structure could be added, on a cloud which could be made from either snow, white wool, or a new cloud block which you can stand on.

In the castle you could find stuff like gold, armour, armour trims and possibly diamonds. The castle would be quite rare though.

There could also be a hostile mob that guards the castle. There also may be unique blocks that the castle could be made of and a unique block as well you could find in a chest in the castle.