St. Mary's Church, world's oldest existing church in S.India.

St.Mary's O.S.Church, India .AD 53. credit:stati.panorama.com
Many westerners, even to day, have no idea whatsoever about the historical background of India's Christian communities that live across this ancient land. Invariably, most of them believe that Christianity was  introduced by the Portuguese first on the Malabar coast of Kerala in the 1600's and this religion had begun to spread gradually in 1700's onward in many parts during the  early colonial rule under the East India company and later under the British Raj.  Though minority in status, in terms of population, Christian communities'  contribution to education  across India has been monumental and they have been in existence in India since AD 53 after the arrival of St. Thomas, one of the prominent  disciples of Jesus Christ. When St Thomas landed in India with a view to spreading Christianity he chose the coastal Kerala region in the South Western Peninsular India.  It is said that Thomas the Apostle,  landed in Muziris, Kerala in AD 52 and  then traveled along the coast to Goa spreading the word of Christ in other parts of India.
Thiruvithamcode Arappally or Thomayar Koviltripadvisor.com
Thiruvithancode, (Thiruvithankodu), a small town in the Kanyakumari district of the Indian state of Tamil Nadu, is about 20 km from Nagercoil, and 2 km from Thuckalay. This town is  famous for St Mary's Orthodox  Syrian  Church (Thiruvithamcode Arappally),  which is believed  to  have  been  established  by  St. Thomas  in  the  first century AD, along with  seven  other  churches (Ezharappallikal)  in Kerala. 
Thiruvithancode was then part of Travancore state and soon after India's independence, it became part of Tamil Nadu state. 

The entrance  to  the  church  was  built  in  the  20th  Century  and  there  are three  main  parts  constructed  in the 17th century.

Tri-lingual name board. St.Mary's O.S.church, India credit:bp.blogspot.com
According  to Issac  Arul  Dhas  of  Scott  Christian college, Nagarcoil,TN (2010), though the Saint Thomas  tradition  of  Indian  Christianity  cannot be  verified  as  historical,  there was  a  tradition of  Thomas  traveling  to India  from  the west at least  in the 3rd century (Acts of Thomas), and there  is an  independent  confirmation  of  the existence of a Christian church in India from the 6th century.

Hence, Kerala  and the bordering  areas in Tamil Nadu on the east along the state line have the distinction of being one of the oldest seats of Christian communities in the world. Subsequently, St.Thomas  moved across other parts  of India for the purpose of missionary work. Subsequently he attained  martyrdom in  in St. Thomas Mount, a suburb of  Madras  city (now Chennai) where his relics are enshrined.

The Indian natives had close relationship with the minority community and the local rulers were helpful to the evangelists for building churches, etc. Roman Catholicism was first introduced to India by Portuguese, Italian and Irish Jesuits in the 16th century to preach the gospel of Jesus Christ among Indians. Most Christian schools, hospitals, primary care centers  came up here through the Roman Catholic missions brought by the  European colonists.  Later after the arrival of Portuguese   hardcore  preachers  from Portugal  there developed a big crack between the natives and the evangelists/ preachers. Religious persecution and suppression of native religion - Hinduism began on a large scale in Goa and part of Kerala by missionaries like St. Xavier. The Goa inquisition was a black chapter in the European colonial history in India and the evangelists had let lose an orgy of violence against the natives including already converted Christians in the name of religion. Consequently,  the Christian  missionaries from Europe earned the ire of the local chiefs and rulers. It took a while for the later missionaries to earn the good will of the natives and the rulers.

Thiruvithamcode Arappally or Thomayar Kovil built by  St. Thomas is  also called Amalagiri church,  named by the Chera King Uthiyan Cheralathan.  Being one of the  world’s oldest churches still daily prayers  are held and the old tradition is being maintained

Ref:
Issac Arul Dhas, `Kumari Mannil Christhavam`(Tamil), Scott Christian College, Nagercoil, 2010,ISBN 978-81-8465-204-8 , Page:7