WARNING, Hoard of the Dragon Queen Spoilers!
In Episode 8: Castle in the Clouds,
the players get a chance to commandeer Skyreach Castle.
One of the commands is for the castle to move in a cardinal direction, but it doesn't state how fast it moves.
I know it's less than 80ft, because
the sidebar on Wyvern Riding and Castle Catching says:
Wyverns are faster than the castle in flight, and they can catch up to it.
And that it is at least 10ft, because
It can Rise and Sink at a rate of 10 feet per round.
For reasons, I need the exact speed of the castle, whether it is written somewhere in the jumbled module, or there's guidance from a different module (maybe Storm King's Thunder?), or if you've personally ruled a particular speed (if you did, please tell me how it went!).
Hurry, the PCs are catching up.