The Aravalli Hills

Go east from the Thar and you reach the Aravalli Hills.

They are among the oldest mountains in the world: about 2.5 billion years old! The Himalayas are about 50 million years old, so the Aravallis are roughly fifty times older.

And they look it. Old mountains get worn down. The highest peak, Mount Abu, is over 1700 m, but most hills are only 300–900 m. They run through Delhi, Rajasthan, Haryana and Gujarat. A drive of about 4½ hours takes you from green Mount Abu to Jodhpur in the desert: a completely different land.

Their most important job: they are a natural barrier that stops the Thar Desert spreading east. Think of two walls: the Himalayas keep the cold winds out, and the Aravallis keep the desert in.

They are rich in marble, granite, zinc and copper, mined for centuries. Ancient mines at Zawar show that over 800 years ago, Indians were the first in the world to master the tricky process of getting zinc out of rock.

Famous forts were built on these hills: Chittorgarh, Kumbhalgarh and Ranthambore. High up, they were hard for enemies to attack.