 In an effort to further improve trade, Darius built canals, underground waterways and a powerful navy.He further improved and expanded the network of roads and way stations throughout the empire, so that there was a system of travel authorization for the King, satraps and other high officials, which entitled the traveller to draw provisions at daily stopping places.While there is no general consensus in scholarship whether Darius and his predecessors had been influenced by Zoroastrianism, it is well established that Darius was a firm believer in Ahura Mazda, whom he saw as the supreme deity.