What geographic feature dominates the southern two thirds of india?

The correct answer is The Deccan Plateau

It is almost the entirety of India and is the largest part of the peninsula. In the northern parts there are mountains because of the Himalayas, but the entire southern region, two thirds of India, is the Deccan Plateau which shares the geographic features of other great plateaus. It has historically been the place where the Hindu culture developed and where many different empires rose and fell before India became what it is today. The word Deccan comes form sanskrit and itself means Southern, which is basically the southern plateau of India.

At the height of 330ft and about 3,300ft, the Deccan Plateau dominated the southern two thirds of the Indian subcontinent. This forms a somewhat triangular shape close to the southern Indian coastline.