Nagarjuna Sagar Dam

Nagarjuna Sagar Dam is the world's largest masonry dam by volume of construction material — built using 1.07 million cubic metres of cyclopean masonry (large-stone-set concrete). Located on the Krishna river straddling the Telangana-Andhra Pradesh border at the historical Buddhist site of Nagarjunakonda, the dam was completed in 1967 after 12 years of construction beginning in 1955.

The dam was constructed primarily by manual labour — at peak, 70,000+ workers laid stones into mortar by hand, using techniques inherited from medieval Indian temple construction adapted for modern engineering scale. This was a deliberate choice by then-PM Jawaharlal Nehru to maximise employment generation in the post-Independence period — automated dam construction would have employed only a fraction of this workforce.

The 124 m tall × 1.55 km long dam impounds 11.47 cubic km of water — the third-largest reservoir in India by capacity. Two underground hydroelectric stations (816 MW total) feed the Andhra Pradesh and Telangana grids, while two main canals (Right Canal + Left Canal) irrigate over 8.6 lakh hectares.

The site has historical significance: Nagarjunakonda was a major Buddhist scholarly centre between the 1st and 4th centuries CE, with Acharya Nagarjuna (the influential Mahayana Buddhist philosopher) believed to have taught here. The dam's reservoir submerged the original archaeological remains, but key sculptures were rescued and reconstructed on Nagarjunakonda island, now an open-air museum reachable by ferry from the dam.