I am one of the oldest in the world, but oldest in India.
I am one of the main resources for the Back Bone of India.
I am a word with eight letters.
the opposite of 'SANE' and reverse the word.
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I think the answer is
I am one of the oldest in the World, but oldest in India.
Kallanai is listed as the fourth oldest dam in the world and the oldest in India still in use.
I am one of the main resource for Back Bone of India.
The backbone of India is agriculture. The purpose of the Kallanai is to divert the waters of the Kaveri across the fertile delta region for irrigation via canals.
The antonym of 'sane' could be 'mad' which, when reversed, becomes 'dam'.