Chapter XXV: Book XV: ch. 21.--Concerning the Indian Dragon

Alexander (while he attacked or devastated some portions of India, and also seized others), lighted on, among other numerous animals, a dragon, which the Indians, because they considered it to be sacred, and worshipped it with great reverence, in a certain cave, besought him with many entreaties to let alone, which he agreed to. However, when the dragon heard the noise made by the passing army (for it is an animal endowed with a very acute sense of hearing as well as of vision), it frightened and alarmed them all with a great hissing and blowing. It was said to be seventy cubits long.

It did not, however, show the whole of itself, but only exposed its head from the cave. Its eyes were said to have been of the size (and rotundity) of a Macedonian shield.