Because it was no longer needed for defensive purposes.
The Tower of London is surrounded by a (dry) moat.
The tower of London's moat was drained because it would soon dry out anyway.
Sharks and tropical fish
The Tower of London does not have any moats.The moat at the Tower of London is still there although it no longer has any water in it.
To defend London
The height of the Tower of London is 27 meters or 90 feet high. The tower is located in central London and can be seen from the River Thames.
The moat is filled with sharks
No, its a pre-stressed concrete box bridge.
The water-filled trench around a castle is called a moat.
Water
It's called a moat, and it is usually filled with water.
A disused moat on three sides and the River Thames on the fourth side.