The water-filled trench around a castle is called a moat.
I think that the 'trench' you are thinking of is a moat. You could say that it is a trench full of water that surrounds the castle. If you are not thinking of a moat then I am sorry.
A moat surrounded the castle.The moat was a form of defence for castles.
Into the Moat was created in 2001.
Advantage of a water moat
Ryan Moat's birth name is James Ryan Moat.
The moat cleaners. ;)
The moat is filled with sharks
Ryan Moat is 5' 9".
A moat is a body of water that circles a castle, and a drawbridge is part of the castle that lowers to allow people to cross the moat.
some animals use a moat
Farther of jamie moat he is, as the sun people call him, "a"