With Tuesday marking 500 days to go before Rio stages South America's first Olympic Games, the city - in fact, all of Brazil - is straining at the leash to be ready.

In having to overhaul crumbling infrastructure, polluted waters and protests notably over the choice of a nature reserve to host the return of golf to the Games, organizers could almost be forgiven for seeing the undertaking as one mammoth discipline - a giant obstacle course fraught with ongoing problems.

Last April, International Olympic Committee vice-president John Coates slammed preparations as the "worst ever" and warned "the situation is critical on the ground" following several inspection visits.