The stupa-monastery complexes were usually located near urban centres, and along major trade and pilgrimage routes. Some marked places connected with important events in the life of the Buddha. Most of the major stupa-monastery complexes were located on the outskirts of great cities of the time— Sanchi outside Vidisha, Amaravati outside Dharanikota (the Satavahana capital) and Nagarjunakonda outside Vijayapuri (the Ikshvaku capital). Stupas were Buddhist commemorative monument usually housing sacred relics associated with the Buddha or other saintly persons. The hemispherical form of the stupa appears to have derived from pre-Buddhist burial mounds in India. Ashoka played an important role in popularizing the Stupa cult.