Behind San Thome Cathedral is the entrance to the weirdly chintzy tomb of St Thomas the Apostle.
It's believed that, in AD 52, 'Doubting Thomas' introduced Christianity to the subcontinent, before being martyred at St Thomas Mount, Chennai, in AD 72. Most of his mortal remains are believed to now be in Italy, but a small cross on the chapel wall containing a tiny bone fragment is labelled 'Relic of St Thomas'.