The chronological order of these prominent stupas based on their significant phases of construction and artistic development is generally considered to be: 1. Bharhut Stupa Primarily associated with the Sunga period (c. 2nd century BCE). Its railing and gate sculptures are considered among the earliest surviving Indian Buddhist art. 2. Sanchi Stupa While its foundation dates back to Ashoka (3rd century BCE), the famous gateways (toranas) and railings, which represent its most elaborate phase, were added later during the Sunga and Satavahana periods (mainly 1st century BCE). Stylistically, the Bharhut sculptures are often placed earlier than Sanchi. 3. Amravati Stupa Flourished under the Satavahana dynasty, mainly between the 2nd century BCE and 3rd century CE. Its peak artistic phase is later than Bharhut and Sanchi. 4. Dhamekh Stupa The present structure in Sarnath is mainly a Gupta period (c. 6th century CE) construction, built on the site of an earlier structure. It is considerably later than the other three.