Giri Durga is one of the categories of forts. It finds
mention in Arthashastra, Manusmriti, Mahabharata and Vastushastram. As per
Arthasastra, Giri Durga 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.
Giri Durga 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 Kalinjar 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.
Giri Durga 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.