Madukkarai Wall

The Madukkarai Wall is a historic border fortification demarcating the boundaries of the three ancient kingdoms of Chera, Chola, and Pandya. The wall was supposedly erected by the goddess Sellandiyamman and may have been built as early as the 1st century AD.
Historic border fortification.
The Madukkarai wall is a stone and earthen fortification with a parallel embankment in central Tamil Nadu. The wall was built during the pre-Sangam period to demarcate the trijunction of the Chera, Chola and Pandya kingdoms. People of this region believe that the Goddess Sellandiyamman miraculously erected the wall overnight to prevent border disputes. The Goddess is said to be a representation of Ujjain Mahakali. Statues of border deities along the wall symbolically guard the frontier.
The border between the Chera i.e. Kongu Nadu and Chola Nadu is demarcated by the Karaipottanar river.
The Karaipottanar river is a tributary of the Kaveri river to the north. The temple of Madukkarai Sellandiyamman at Mayanur (Tamil Nadu) is the culminating point of the wall. The wall ends at Madurai Meenakshi Amman Temple.
Importance.
The wall is described as of historic importance in the 1907 (British era) gazetteer of Madras:
The wall is of unknown age, but could be as old as the 1st century AD:
The wall still demarcates the boundary between the Karur and Kulithalai taluks (districts) and after that, between the Dindigul and Tiruchirappalli districts.