Nandi Hills or Nandi betta (Anglicised forms include Nandidurg and Nandydoorg) is an ancient hill fortress in southern India, in the Chikkaballapur district of Karnataka state. It is 10 km from Chickballapur town and approximately 60 km from the city of Bengaluru. The hills are nestled near the town of Nandi. In traditional belief, the hills are the origin of the Arkavathy river, Ponnaiyar River, Palar River and Penna River.
