RIO (REUTERS) - Workers, engineers and window cleaners are in full swing at Rio's Olympic Park as they put the finishing touches ahead of the Games.

The first Olympics on the South American continent start August 5, and organisers are still frantically rushing to prepare venues.

Half a million people are expected to visit Rio over the next three weeks, but the Games being are being overshadowed, not only by the Zika virus but also concerns over crime and delays to infrastructure.

The metro that will carry visitors from the city centre to the distant suburb where the Games are held was inaugurated only on Saturday (July 30), and the main ramp at the sailing centre collapsed also on Saturday, adding another headache to last-minute preparations.

Follow ST's Olympics microsite and ST's team heading to Rio.