地下密牢

例句：

1. 1. The criminal was sentenced to life in the underground prison.
   这名罪犯被判终身监禁于地下监狱。
2. 2. The underground tunnels were used for transportation during the war.
   在战争期间，这些地下隧道被用来运输物资。
3. 3. The underground mines are a hazardous environment that requires special safety measures.
   这些地下矿井是一个危险环境，需要特殊的安全措施。