Brahma’s son Kusha had four sons with the princess of Vidarbha – Kushamba, Kushanabha, Asurtarajas, Vasu. As per their father’s instructions, each of them built a city and started living there. Kushamba built Kaushambi, Kushanabha Mahodayapura, Asurtarajas Dharmaranya and Vasu Girivraja as per Ramayana Balakanda Sarga 32. As per Kathasaritasagara, Kaushambi was at the centre of a kingdom named Vatsa and Udayana, a descendant of the Pandavas, ruled from here for a while.