I don't know which place in South India you would like to visit.. But I'll tell you some of the best treks in Karnataka.. 1. Kanoor fort trek - 3 days
2. Kodachadri trek - 2 days
3. Kumara Parvata trek - 2 days
4. Mullayanagiri trek - 2 days And still many are there.. All of these are at a over night journey distance from Bengaluru..