This 1967 cover photo depicts construction of the Nagarjunasagar Dam in India. The three-mile long gravity dam, with a central masonry section almost one mile long, flanked by earth and rockfill embankments, was built almost entirely by hand.

Tower cranes were used, but workers carried baskets of mortar up ramps supported by bamboo scaffolding and spread it in 2-in. layers.

Then other workers placed 2.5-cu-ft stone blocks on the fresh mortar and vibrated them by hand to get a firm fit. The mortar was surki, a powdered burnt clay mixed with sand, that was cheap and readily available, while cement was scarce and expensive in India.

The workforce in 1967 was 50,000, including both men and women. Two associated aqueducts that channeled the water from the reservoir created by the dam to irrigate large swaths of farmland had a separate workforce of 80,000.

Construction lasted from 1955-69. At 411 ft tall, it was the tallest masonry dam in the world when completed.