‘险要’ (xiǎn yào) is an adjective describing a location—typically a geographical feature like a mountain pass, gorge, or fortress site—that is both difficult to access (‘险’ meaning ‘perilous’ or ‘steep/dangerous’) and critically important for defense or control (‘要’ meaning ‘essential’ or ‘strategic’). Together, the characters convey the idea of a place where natural difficulty combines with military or logistical significance.

This term is most commonly used in historical, geographical, and military contexts—especially when discussing ancient battle sites, frontier defenses, or terrain analysis. It carries a formal, literary tone and rarely appears in casual speech. You’ll find it in textbooks, documentaries about Chinese history, and descriptions of scenic but historically charged landscapes—such as the Great Wall’s watchtowers or the Yangtze River’s Three Gorges region.