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Madukkarai (Madhilkarai Tam: மதுக்கரை, மதிற்கரை - மதில்கரை, அருங்கரை, வாங்கரை) lit. is stone and earthen fortification and a parallel embankment in central Tamil Nadu, built during the Pre-Sangam period to demarcate the trijunction of Chera, Chola and Pandya countries. People of this region beleieve that the Goddess Sellandiyamman (Tam: செல்லாண்டியம்மன், செல்லியாண்டியம்மன், செல்லாயி, செல்வநாயகி, செல்லம்மா, செல்லாத்தா) erected the wall overnight to prevent border disputes. The Goddess is said to be a representation of Ujjain Mahakali.
Utsava Murti of Madirkkarai Sellandi
The border between the Chera i.e (Kongu Nadu) and Chola Nadu is demarcated by the Karaipottanar (கரைபோட்டானாறு),
"The name signifies ' the river which marked the boundary,' and native tradition, which appears to be founded on fact, says that the stream was once the boundary between the Pandya, Chola and Chera kingdoms. Beyond the Cauvery, an embankmect runs southwards across the Kulittalai taluk, and this is supposed to be the continuation of the boundary."
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 and the wall ends at Madurai Meenakshi Amman Temple.
Even the British era gazetteers of Madras mentions the wall:
"A bank runs south from the river at this point and is said to have been erected to mark the boundary of the Chola and Chera kingdoms."
"A stanza ascribed to the poetess Auvaiyar^ (whom Mr. Kanakasabhai assigns to the Ist century A.D.) gives the boundaries of the Chola kingdom as the sea on the east, on the north the Pennar river (which reaches the sea near Cuddalore), on the south the Vellar (near the southern border of the Tanj ore district), and on the west Kutagiri, Kottagiri, or Kottaikarai. The last of these names means ' fort bank ' and tradition says that it refers to the great embankment of which traces still stand in the Kulittalai taluk. The Karaipottaudr river (see page 8) is also supposed to have formed part of the boundary and to have obtained its name from that fact. 
The wall still demarcates the boundary between the Karur (சேர கொங்க தேசம் [மேனாடு] - தட்டய நாடு) and Kulithalai taluks (சோழ தேசம் [பொன்னிவளநாடு] - கோனாடு - கூத்தாழை நன்னாடு) and after that, between Dindigul district and Tiruchirappalli districts.
 Structure of the wall
A section of the wall near Manavasi
The wall is a rock and earthern wall six feet to six feet if hight and breadth on the Kongu Nadu side. An adjoining embankment around thirty feet wide runs alongwith the wall on the Chola Nadu side. The wall is in fragments as most of it has been used for building material in recent times though there is an ancient curse attached to it. Locals still call it கரை or மதுக்கரை.
The entire way is dotted with border deities who guard the frontier.
This heritage ancient structure is ignored by the Indian and Tamil Nadu state governments thereby leading to incessant quarrying and mining. Locals fear a conspiracy by the government to destroy the wall.
2. ^ http://wikimapia.org/#lat=10.9599625&lon=78.2427192&z=16&l=0&m=b&search=madukkarai%20sellandiyamman
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