Giridurga is one of the categories of forts. It finds mention in Arthasashtra, Manusmriti, Mahabharata and Vastushastras. As per Arthasasthra, Giridurga is to be located atop a hill or in the caverns of a hill. Majority of Giridurgas had Hindu temples and sacred places associated with saints.
Giridurga was the strongest defensive measure in the ancient world as its location makes it naturally inaccessible.
In the ancient world, the kingdom of Chandelas was defended by eight hill forts of which Kainjar was the strongest.
Kingdoms in the Sahyadri and Aravali ranges had erected a number of hill forts. Hill forts can be seen today in Maharashtra, Rajasthan and Madhya Pradesh.
It was nearly impossible to win a hill fort through assault. They were usually annexed through bribery or sieges.
Giridurga of ancient India were of different shapes – square, circular or rectangular. They had parapets and watchtowers. They also had outside obstructions like knee-breakers, mounds of earth, pits, ditches filled with thorns and covered with sand and tridents.