Complex sentence: From the 3rd century until the 5th, Christianity was consolidated in the area of Canzo; the dedication of a church in Canzo's territory to St. Stephen, the first martyr, whose cult was spreading in primitive Christianity, most probably dates to this age.
Split into simpler sentences: From the 3rd to the 5th centuries, Christianity was consolidated in the area of Canzo. The first martyr, whose cult was spreading in primitive Christianity, most probably dates to this age.