There was direct maritime trade between the Roman Empire and China’s Han dynasty as early as the reign of Marcus Aurelius. The Han court sent an ambassador by sea (aboard a Chinese vessel, probably a small fleet of ‘em) and arrived in the Persian Gulf, alas, too late to make direct contact (the pederast Hadrian had abandoned Trajan’s province of Mesopotamia), so they worked out some trade deals with the locals and went home. Roman trade by sea was on an enormous scale, particularly with India.
The Apostle Thomas (of Doubting fame) went all the way to India where he was executed.
I remember reading (perhaps here) about an ancient Chinese Temple that was found to have been built upon the remains of a Christian Church. A creche was found hidden away in an attic.