A castle was a fortified residence built mostly in the Middle Ages by nobles, royalty and military orders, usually as the private home of a lord who needed to hold local land. European castles emerged in the 9th and 10th centuries after the Carolingian Empire split into small territories, so each lord built one to dominate the surrounding area, launch raids and protect against rivals. Early castles relied on natural hills and a central keep, but from the late 12th century builders added towers and flanking fire to maximise defence. Once cannon could break stone walls in the 15th century, castles became hard to defend and uncomfortable to live in, and they gave way to star forts and country houses.

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.