Himalayas.
Began forming approximately 50 million years ago; still actively rising today.
A landscape with a history.
Formed by the ongoing collision between the Indian Plate and the Eurasian Plate. India was once a separate landmass that drifted northward and collided with Asia — since neither plate is dense enough to subduct beneath the other, the crust between them has been folding and thickening for tens of millions of years, and continues today, making the Himalayas one of the only major mountain ranges still actively gaining height.
What makes it remarkable
Contains Mount Everest, Earth's highest peak above sea level, along with most of the world's other highest mountains.
Another skyline. Another story.
Andes
Formation began roughly 200 million years ago, with the modern range's major uplift occurring within the last 25 million years.
Rocky Mountains
Primary formation (the Laramide orogeny) occurred roughly 80–55 million years ago.
Appalachian Mountains
Began forming approximately 480 million years ago.