The Cyclopean Wall is an ancient stone fortification located around Rajgir in the Nalanda district of Bihar. It is believed to have been constructed during the period of the Magadha kingdom, around the 5th–4th century BCE. The wall is called “Cyclopean” because it is built with massive, uncut stone blocks fitted together without the use of mortar. Stretching over several kilometers, it once encircled the ancient city of Rajgir. The wall served as a defensive structure to protect the capital from invasions. It reflects advanced engineering and planning of early Indian civilizations. Portions of the wall can still be seen winding through hills and forests around Rajgir. The Cyclopean Wall stands as a remarkable example of ancient military architecture in India.