Solution:Several early historic sites in India, including Mathura, Kotasur, and Atranjikhera, show evidence of mud fortifications. These fortifications, constructed using mud bricks, served as defensive structures for settlements during the Chalcolithic and Early Historic periods. Atranjikhera, in particular, reveals well-planned mud-brick structures and fortifications dating back to the Painted Grey Ware (PGW) culture, indicating early urban development and defense mechanisms.