The planning fallacy is the tendency to underestimate how long a task will take, even when we know similar tasks ran late in the past. The bias mainly affects predictions about our own work, since outside observers tend to overestimate the time needed. Daniel Kahneman and Amos Tversky first proposed the idea in 1979. Later, Lovallo and Kahneman expanded it to cover costs and risks as well as time, and to show that people often overestimate benefits at the same time. The result is that projects routinely overrun on time and budget while delivering less than promised. Planners tend to picture the best case rather than drawing on the messy history of similar projects.

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.