From the summit of Rio de Janeiro's Corcovado Mountain, Guanabara Bay far below glistens with a deceptively inviting azure hue. The bay, which is a designated water-sport venue for the 2016 Summer Olympics, is heavily polluted and has been for decades.
Olympic athletes scouting the bay are alarmed, despite the Brazilian government's assurance that the site will be cleaned up in time for the games.
Will Brazil meet the deadline, and if so, will the cleanup be a temporary fix or have some permanence?
The environmental impact of the Olympics on the host cities in the aftermath of the games is a question often raised. Will that impact be a sustainable upgrade of the surroundings, a Band-Aid, or a step backwards?
Actually, the Olympics' environmental legacy has been mixed. Beijing's reduction of its horrific air pollution during the 2008 Summer Olympics was only a temporary respite created by mandatory factory closures and restricted automobile use. Those draconian measures could not be practically extended past the games. Consequently, the air quality today is worse than ever in the Chinese capital, which has to deal with many more people and vehicles than it did five years ago. Chinese regulators simply were unable to keep up, despite the planting of millions of new trees in the region.
A poor environmental outcome also occurred in the aftermath of the 2004 Summer Olympics in Athens, which left degraded wetlands in its wake.
The Winter Olympics always threatens to inflict alpine erosion in the quest for spectacular ski runs, and the fast-approaching games in Sochi, Russia, are no exception. Will they resemble the 1992 games in Albertville, France, where the competition was situated in a geologically unstable location, leading to major land disturbance?
On the other hand, the 1994 Winter Games in Lillehammer, Norway, was the first Olympics that chose to officially designate itself "green" and then proceeded to back up that claim. An Olympic Hall in the master plan was relocated to spare a bird sanctuary, and a major facility was constructed inside a mountain to preserve an unblemished countryside.
Since 1994, there have been a fair share of post-Olympic environmental success stories. The 2000 Summer Olympics in Sydney transformed a nearby wasteland into a suburb, and an industrial site into a major urban park. In London the 2012 Olympics left a legacy of a major park and urban renewal in down-and-out neighborhoods in the eastern part of the city.
But Rio faces a more formidable challenge from a long history of environmental neglect, exacerbated by prodigious population growth and a lack of adequate sewage disposal. Spectacular beaches are bordered by waters that are hazardous for swimming. Because of decades of insufficient awareness and resources, Rio has much further to go to pass muster than some of its predecessors in more developed countries.
Can Brazil pull it off? The Olympic Committee members are keeping their fingers crossed.
Whatever the 2016 outcome, as the world becomes more crowded and industrialized, there will be greater chance for Olympic environmental disruption. Perhaps the day will arrive when the games alternate between permanent sites on each continent to save nature and money.