Kautilya's Arthashastra 2.4.7

2.4.7

vāstuhṛdayād uttare navabhāge yathoktavidhānam antaḥpuraṃ prānmukham udanmukhaṃ vā kārayet //

In the midst of the houses of the people of all the four castes and to the north from the centre of the ground inside the fort, the king’s palace, facing either the north or the east shall, as described elsewhere (Chapter XX, Book I), be constructed occupying one-ninth of the whole site inside the fort.