Complex sentence: The Kingston Centre's retail traffic, once brisk, sharply declined after the relocation of Sears store to the rival Cataraqui mall in 1999 left Loblaws supermarket (which expanded into a new building on the grounds of the former Sears location) as sole anchor.
Split into simpler sentences: The Kingston Centre's retail traffic, once brisk, sharply declined after the relocation of Sears store to the rival Cataraqui mall in 1999. The Loblaws supermarket, newly-expanded into a modern building on the grounds of the former Sears location, became sole anchor.