奥おく壁へき

noun

inner wall; inner rockface

Refers to the innermost wall or rockface of a cave, mountain valley, or similar enclosed natural space. Often used in contexts like caving, climbing, or describing deep mountain scenery.

• 洞どう窟くつの奥おく壁へきには、古こ代だいの壁へき画がが残のこっていた。

  Ancient murals remained on the inner wall of the cave.

• 谷たにの奥おく壁へきから滝たきが流ながれ落おちている。

  A waterfall cascades down from the inner rockface of the valley.