Mountains or a mountain range; high, often rugged mountainous areas (used in contexts like mountaineering or geography).
その国には美しい山岳が多く、登山客に人気だ。
That country has many beautiful mountains and is popular with climbers.
山岳地帯の気候は変わりやすいので注意が必要だ。
Weather in mountainous regions changes easily, so caution is necessary.
高度のある山岳登山には専門の装備と経験が求められる。
High-altitude mountaineering requires specialized equipment and experience.