South Indian Christian tradition holds that Thomas, one of the twelve disciples of Jesus (you know, Doubting Thomas? yeah, that guy), came by boat to Kerala from Judea in 52 A.D. and preached between 52 A.D. and 72 A.D., when he was martyred on what is now known as St. Thomas Mount, in Chennai.
He is known around these parts as the patron saint of India and is credited with bringing Christianity to the subcontinent.
This is the cave where he is said to have hidden before being killed.
There is also a spring just outside the entrance to the cave. The sign on the stone wall behind it says that it cures diseases, and the lady who tried to get me to drink some of it told me that it was holy water. I had to pass on that. One – I don’t currently have any diseases that I know of that need curing. Two – I wasn’t sure how to explain it when holy water gave me diarrhea. So, I told the lady, as to not disrespect her belief in the holiness of the water, that I don’t think that my belly is so holy.
A Broad Abroad in India 