Old mountains are mountains or mountain ranges that have existed for long geological periods of time. They may be weathered, rounded, and shorter than they once were. They may no longer reach to heights that inhibit plant growth and so may be entirely covered by jungle, forest, or grasslands. If enough weathering has occurred, old mountains may be nothing more than rounded hills. Old mountains are home to hillbillies, sequestered monks, and long forgotten creatures which sleep in their depths.

Old mountains may have other ‘old’ elements associated with them. There may be old mines, old sawmills, or ruins or abandoned structures on them. Rivers may have eroded their surface to form canyons and waterfalls.