Before Priuses, before carrying a plastic water bottle was a sin, Denver was working toward building a sustainable community.  In the 1990s, the city committed to green technology. Now more than 43 percent of the city’s fleet is powered by alternative energy. Sustainable design, a citywide commitment to building up rather than out, historic preservation grants and a commitment to incorporating natural elements into design have led to Denver’s designation as one of the country’s five greenest cities.