In 1625, in digging for a foundation near Siganfu, metropolis of the province of Xensi, was found a stone with a cross on it, full of Chinese and some Syriac characters, containing the names of bishops, and an account of the Christian religion, “that it was brought from Judea ; that having been weakened, it was renewed under the reign of the great Tam,” (cir. A. D. 630.)
Source: wiktionary