any invader coming from the north. It was erased by Tipu Sultan in an act of revenge for having been defeated in his attempt to subdue Travancore in 1789. It had a length of 40 km and extended from the sea near Vypeen Island to the Western ghats. Just before returning to Mysore after his failed attempt, he spent six days to demolish the lines which he called the 'Contemptible Wall'. He had sworn to demolish it earlier after his failed attempt to breach it on 28 December 1789, and lost 2000 soldiers in that single night, due to the spirited defence by the Cadres, for the loss of just a few soldiers of Travancore. Many other forts like the Vattakottai Fort facing the sea near Kanyakumari, the hill-forts of Savakkotta, and the Marunnu Kotta (Ammunition fort) near Padmanabhapuram were built under De Lannoy's supervision. De Lannoy is also credited with the erection of some other small forts and tunnels. Padmanabhapuram fort The palace fort of Padmanabhapuram was constructed for to save the palace and for the safety of the king who lived in the Padmanabhapuram palace. The fort has an area of 187 acres. The Padmanabhapuram fort was built with mud originally was disassembled and reconstructed with granite rocks. The height of the walls varies from 15 feet to 24 feet according to the inclination of the ground. The thickness of the fort wall was 35 feet. Udayagiri fort The Udayagiri Fort is situated nearly one kilometer away from Thuckalay. De-Lannoy reconstructed and fortified the fort at Udayagiri, which was built in 1742 A.D. The Udayagiri Fort walls and ramparts which are 18 feet high and 15 feet thickness with parapets averaging 4 feet in height are faced with huge blocks of well arranged granite. The space between the inner and the outer ramparts consisted of mud. Besides the gateway there are smaller doors near three bastions. The Udayagiri Fort served as a military base during the reign of Marthanda Varma which was supervised by Captain De-Lannoy Cannon Factory He built a factory to produce war materials such as cannon balls. These were heavy artillery materials made of pure iron. The weight of such cannon balls ranged from 30 kgs to 1800 kgs. Vattakkottai De Lannoy repaired and strengthened the old fort that was built by Pandya kings. Vattakottai Fort is a specially built fort on the sea coastline