Construction of forts which are to take place in every four quarter of the kingdom can be of four types. As described in Arthashastra the forts can be water -fortification like an island in the midst of a river or a lake, or a plain surrounded with low grounds; mountain - fortification with rocky tracts or cave; a desert fortification made at the midst of barren land devoid of water; or forest fortification with full of wet land, water and thickets. The selection of fort shall depend on the topography of the kingdom according to which the strategies for security will depend. Among these Kautilya suggests water and mountain fortification are the best suited to defend the populous centres while desert and forest fortification are best for habitation in wilderness. Further the forts should be surrounded be deep canals of water made by digging 6ftdeep canals surrounding the fort form all corners. The ditches can be as deep as 6ft, 14ft and 12 ft in depth and up to less than one -quarter or even one-half of their width. It can be either circular or square in shape surrounded with artificial canal of water, well connected with land and water paths.
Construction of forts then inserts that at a distance of 24ft from the inner most ditches a rampart of mud is to be built in order to make it connected which shall have poisonous bushes around its bank. On the top of it parapet of stone slabs are to be fitted at the gap of 12 to 24 hastas. Chariots are to be moved on the trunk of palm trees and moveable towers with movable staircases will be constructed as well. Overall Kautilya with the detailed description of fortification tries to highlight the risk of the king as well as his kingdom which existed during that time which could be avoided only with creation of strong fortification. He further gives a detailed picture of the fort itself with number of floors to be included .While in the first floor there shall be a big hall known as 'sala' in which the Sabhas will be held; the other storeys will include hidden walls and pillars having hidden staircases which shall help in easy escape at the time of crisis.
Thus, construction of forts had been considered to be the most vital and primary job of the king and his ministers in order to provide security to the people as well as the royal family. As such it lays down in detail all the elements to be used for the construction of the fort to keep it unconquered by the enemies.