One of the oldest stupas is the Great Stupa at Sanchi, in central India. 

The world-famous stupa was first built in brick by Mauryan emperor Ashoka of the 3rd century BCE  was later extended in stone to twice its original height.

Stupa architecture includes:

• A hemispherical mound at top (Anda): The domed shape recalls a mound of dirt that was used to cover the Buddha’s remains.
• A square railing (harmika): The harmika is inspired by a square railing or fence circling the dirt mound, marking it out as a sacred burial ground.
• A central pillar supporting a triple-umbrella form (chattra): In addition, the chattra was derived from umbrellas placed over the mound to protect it against the elements.
• Enclosure wall with decorated gateways at the cardinal directions (toranas): The wall with three horizontal stone bars with its signature-surrounds the entire structure.
• A circular terrace (medhi): The terrace surrounded by a similar railing with three bars supports the anda and lifts it off the ground.