mountains and seas
Refers to the natural world of mountains and seas, often used in literary or poetic contexts, or in compounds like 山海の珍味 (delicacies from land and sea).
山海の自然を満喫する旅に出た。
I went on a trip to fully enjoy the nature of mountains and seas.
この店は山海の珍味が自慢だ。
This restaurant prides itself on delicacies from land and sea.