Śeṣācala
The seven hills
The rings behind the head are not a halo in the ordinary sense. They are Śeṣācala — the seven hills of Tirumala, which are Śeṣa himself in the form of a mountain. In Vaikuṇṭha the Lord rests on the serpent; at Tirumala he rests on the hill that is the serpent.

