Sri Ranganathaswamy Temple at Srirangam is one of the great temple complexes of India. Dedicated to Vishnu as Ranganatha, it covers a vast area of courtyards, pillared halls, shrines, tanks, and towering gopurams.
This is a working pilgrimage centre, not a quiet ruin. Give it time, dress conservatively, and be prepared for areas where non-Hindus cannot enter. Even from the accessible courts, the scale and continuity of worship are extraordinary.