34 MILES(56 KMS)LONG FORT(ALSO KNOWN AS TRAVANCORE LINES/KRISHNA KOTTA)

PALLIPURAM KOTTA ,THE STARTING POINT OF THE GREAT WALL& LATER
FORT DESTROYED BY TIPU SULTAN

Nedumkotta or Travancore lines was a wall built as a protection against
consistent invasion and threats from northern kingdoms mainly Zamorins of Kozhikode. It was built by the Dharma Raja Karthika Thirunal, King of Travancore with the support and permission of the Kingdom of Kochi.

The Zamorin of Kozhikode had long standing enmity with the kingdom of Kochi. The Zamorin had usurped Kochi's native Village. This led to dispute and then wars. With the stature and strength of Zamorin, he became a threat not only to Kochi but for Travancore too. Hence it was decided to construct a defence fortification jointly with the help of British. This led to the building of the wall across the kingdom from the sea to the Western Ghats. It was completed before 1766. Later the Zamorin was defeated and kingdom came under Hyder Ali, the army commander of Mysore. The Nedumkotta stood as a barrier between the invading forces of Tipu Sultan to run over both Southern Kingdoms.The fort was designed by the Army Commander De Lennoy under the supervision of Ayyappan Marthandan Pillai, Dalawa of Travancore and Komiachan, Minister of the Kochi Kingdom.

The structure
The wall was 56 km (36 miles) long. It started from Pallipuram Kotta near the sea, touches kottamukku, krishnankotta and extended till the Foot hills of the Anamalai in the Western Ghats. The Chalakudy river and lagoon which falls on the alignment was left alone as they themselves were a barrier. A trench 20 feet (6.1 m) deep and 16 feet (4.9 m) wide was built along the northern side of the wall for the full length. At some places the wall reached 50 ft (15 m) in height. Hollows were made inside where about 100 soldiers could hide and make an ambush. A company of soldiers was stationed about every kilometer with ammunition store house at strategic points. There were also caves in the nearby wells to hide in the possibility of an unannounced attack.
The places where fortification once stood is in the present Mukundapuram Taluk in Thrissur District, Kerala.

Attack of Tipu Sultan and its Destruction
24 years after his father, Hyder Ali had attacked Kochi, Tipu Sultan started on a conquest to conquer Kochi and Travancore. On December 28, 1789 Tipu attacked the fort and gained entry but was ambushed by the Travancore army and had to retreat. Later in April he came back with reinforcements and this time was able to break in to the territory after making the way through the Nedumkotta. He destroyed the wall at Konoor kotaa or kottamuri and advanced further. He filled trenches for a few kilometers so that his army could advance. By this time he received information that the British army was planning an attack on Srirangapatnam and had to return back.
The most portions of the wall was destroyed during war, later eroded away due to heavy rains and trenches were filled up. The most of the ruins whatever left have also been lost due ignorance about the historical structure among the locals.