Engineering skills were evident in this period as proved by the remains of famous dam built for the irrigation works during Chandragupta Maurya's period and repaired by Saka king Rudradaman. Another remarkable structure is a complex of four water tanks at Shringaverapura, which reflects a very advanced level of hydraulic engineering. In Shringaverapura structures, tanks were built of millions of bricks and water was brought from the river Ganga through a canal measuring about 250 mts in length and 38 mts in width. It had the capacity of about eighty lakh litres of water. Indian astronomers had developed an elaborated astronomical system after modifying and adopting more accurate values by counting the periods of revolution of the sun, the moon, the five planets, and the two nodes, namely Rahu and Ketu. Eclipses were also predicted with an accuracy. Pancha Siddhantika written by Varahamihira, gives the summary of five schools of astronomy present in his time.