Aadisesha is the seat on which Lord Srimannarayana rests in his abode Sri Vaikunta. In Tirumala hills the Seshachala range is believed to be the manifestation of Divine serpent, Aadisesha. That is why it is also called Seshachala.
From a distance, Tirumala hills appears in serpentine form. Legends say that In Tretha Yuga, during Sri Ramaavathara, Aadi Sesha took the incarnation of Lakshmana Swamy, while in Dwapara Yuga during Sri Krishnaavathara he took the form of Balarama.