Complex sentence: This limited use of stone, as a supplementary building material, was most prevalent in Lesser Poland and was made possible by an abundance of limestone in the region--further north in the regions of Greater Poland and Pomerania the use of stone was virtually nonexistent.
Split into simpler sentences: This limited use of stone, as a supplementary building material, was most prevalent in Lesser Poland and was made possible by an abundance of limestone in the region. While further north in the regions of Greater Poland and Pomerania the use of stone was virtually nonexistent.