The Denver City Council took a major step Monday toward clearing the way for Denver Nuggets and Colorado Avalanche owner Stan Kroenke to build new skyscrapers on the expanse of parking lots around Ball Arena where those teams play. They also ensured the teams will stay on Kroenke-owned land in central Denver for another quarter century. The ability to construct buildings as tall as 30 or 40 stories around the arena is a critical component of plans to greatly expand downtown Denver.