护城河

例句：

1. 1. The ancient city was surrounded by a deep moat, effectively protecting it from attackers.
   这个古老的城市被一个深深的壕沟包围着，有效地保护了它免受攻击者的攻击。
2. 2. The castle's walls were lined with moats and ditches, adding to its defensive strength.
   城堡的墙壁上布满了壕沟和沟渠，增强了它的防御力量。
3. 3. The fortress had several moats and embankments, providing ample room for defense.
   这个要塞有好几个壕沟和护坡，为防御提供了充足的空间。