Complex sentence: Czarnecki decided to demolish the building on June 2,2007 and built the Sky Tower, a 258-metre-tall apartment building, which was completed in 2012.
Split into simpler sentences: Czarnecki decided to demolish the building, which was done on June 2,2007. In its place, the Sky Tower was built, a 258-metre-tall apartment building, which was completed in 2012.