A naturally formed barrier or deep trench that is difficult to cross; often specifically used to describe the Yangtze River [[长江|長江|chang2 jiang1]] as a strategic defense.

(idiom) to learn a lesson from a setback or mistake; to gain wisdom from a bad experience

military trench or entrenchment dug around a position for protection and defense

a path or section of roadbed excavated through high ground for a railway or highway

trench warfare in military contexts

A long, narrow block of the earth's crust that has dropped between two faults, forming a trench or rift valley

Refers to the Yangtze River's role as a strategically important natural defense or moat because of its width and flow.

military trench or defensive ditch used for combat

a ditch or moat; a defensive trench surrounding a city

A massive geological trench stretching from the Red Sea through East Africa, spanning about 4,000 miles to Mozambique.

Fall into a moat and you'll be wiser next time; an idiom meaning one gains knowledge and experience from suffering a setback or making a mistake.

(literary) military fortifications comprising high walls or ramparts and a surrounding ditch or moat

The vast and deep abyss of human desire; often used to describe greed or longing that is difficult to overcome or satisfy.

deep moats and high ramparts; to build strong defensive fortifications

To build high fortifications and dig deep moats; describes an extremely strong defense.