What is a stupa, and what is its function in Buddhism?

What will be an ideal response?

Essay responses should include these points:
• A stupa is a type of burial mound. Originally the stupa held the remains of Buddha.
• The stupa is represented in Buddhism symbolically as the banyan tree under which Buddha found enlightenment.
• The stupa circle-mound represents the diagram of the cosmos.
• Pilgrims circle the Great Stupa at Sanchi, symbolically following Buddha's path.