Sankin-kōtai was a policy implemented during the Edo period in Japan, requiring feudal lords, or daimyō, to alternate their residence between their domains and the capital, Edo. This system aimed to strengthen the central government's control over the daimyō and prevent rebellion by keeping their families in Edo as hostages. The policy also stimulated economic growth and cultural exchange, as daimyō and their retinues traveled to and from Edo, spending money on goods and services. This movement contributed to the development of infrastructure, such as roads and inns, and fostered a vibrant urban culture in Edo.