The most impressive of all cobras, and perhaps the most impressive of all snakes, is the king cobra of Southeast Asia. It's the largest of all venomous snakes, attaining a length of 18 feet and a weight of over 20 pounds.The king cobra is the only known nest-building snake. the female builds an 18 inch-high,two-compartment nest of grass and leaves on the forest floor.the lower compartment contains the eggs, and the upper houses the female,who guards the clutch until it hatches.