Mbh 12.86.2a

"'Bhishma said, "It is proper, O Bharata, to enquire about the conduct that should be followed and the defences that should be adopted with respect to the city in which, O son of Kunti, a king should reside. I shall, therefore, discourse to thee on the subject, referring especially to the defences of citadels. Having listened to me, thou shouldst make the arrangements required and conduct thyself attentively as directed. Keeping his eye on the six different kinds of citadels, the king should build his cities containing every kind of affluence and every other article of use in abundance. Those six varieties are water-citadels, earth-citadels, hill-citadels, human-citadels, mud-citadels, and forest-citadels.[247] The king, with his ministers and the army thoroughly loyal to him, should reside in that city which is defended by a citadel which contains an abundant stock of rice and weapons,--which is protected with impenetrable walls and a trench, which teems with elephants and steeds and cars, which is inhabited by men possessed of learning and versed in the mechanical arts, where provisions of every kind have been well stored, whose population is virtuous in conduct and clever in business and consists of strong and energetic men and animals, which is adorned with many open squares and rows of shops, where the behaviour of all persons is righteous, where peace prevails, where no danger exists, which blazes with beauty and resounds with music and songs, where the houses are all spacious, where the residents number among them many brave and wealthy individuals, which echoes with the chant of Vedic hymns, where festivities and rejoicings frequently take place, and where the deities are always worshipped.[248] Residing there, the king should be employed in filling his treasury, increasing his forces, enhancing the number of his friends, and establishing courts of justice. He should check all abuses and evils in both his cities and his provinces.