As protection from raiding elephants.
Build a moat
They mostly used rossetta stone and limestone :)
He built massive city walls and a moat
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.
As protection from raiding elephants.
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.
because it has a hill with a castle on top and a water river type thingy around it