RIO: From the glorious Maracana stadium to a sewage-filled bay, a huge variety of settings will greet athletes and sports fans at the Rio Olympics in six months.

This is the first time a South American city has hosted the Summer Games and the challenge has been made all the harder for Brazil since the economy went into freefall.

The good news is that almost all stadiums and arenas are either complete or 97 per cent ready, according to organisers. But with Brazil's recession showing no letup, the pressure is on.

Tale of four cities

Brazil's most iconic city has been split into four hubs for the Games.

The main complex is the Olympic Park in the well-off western Barra de Tijuca area, which notably will have the tennis, most swimming, gymnastics, judo and wrestling events.

Deodoro, a modest neighborhood in the northwest of Rio that doesn't usually see many tourists, will have sports including riding, field hockey, rugby sevens and canoeing.

Sailing, rowing, long-distance swimming events and beach volleyball will be held at or near the famous Copacabana beach in southern Rio.

Some of the most glamorous events — the opening and closing ceremonies and athletics competitions — will take place in two northern football stadiums: the famous Maracana and the Joao Havelange stadium, now also called the Olympic Stadium.

The football tournament will be spread around the country at former 2014 World Cup sites, before final rounds concentrate in Rio at the Maracana and Olympic stadiums.

Olympic Park progress, problems

The nearly finished Olympic Park includes the 19,750 seat tennis center, the 18,000 swimming center and the Maria Lenk diving and synchronized swimming pool.

The velodrome, with 5,000 capacity, is one of the few sites where work is dragging on, with only 80 per cent completion. The tennis center is 97 per cent ready, but the mayor's office recently broke off the building contract, citing poor work.

The Olympic Village, a complex of apartment buildings that will house the 18,000 Olympic and Paralympic team members, is near finished.

There has been controversy after a low-income neighborhood nearby was bulldozed last year to make way for the construction. There have also been questions about the golf course built in the Olympic Park on an ecologically sensitive site.

Not plain sailing

Sailing and windsurfing will be based at Marina da Gloria, with the courses out in Guanabara Bay. Aquatic marathon and triathlon swimming will take place off Copacabana beach.

Decades of pollution have put the beautiful Guanabara Bay in danger of ecological ruin and there are fears for the health of athletes.

Authorities promised a huge cleanup, with reform of the city's sewage system so that at least 80 per cent of sewage reaching the sea would be treated.

That goal was abandoned and ecologists say that currently no more than 50 per cent of sewage is treated.

Guanabara Bay also sees vast amounts of floating garbage, such as plastic bags and bottles. Trash-collecting boats will encircle the sailing courses to try and prevent anything getting in the way of the speeding boats.

Economy sinks floating seats

Economic downturn and more than 10 per cent inflation has forced organisers to cut their budget by around 10 to 30 per cent.

One of the victims was a 4,000-seat grandstand that would have floated on the lagoon, called Lagoa Rodrigo de Freitas, where rowing and canoe sprint will take place.

There were reports of similar cuts at the 12,000 capacity beach volleyball grandstand.

The game is one of the most popular in Brazil and will take place on Copacabana beach, where dozens of amateur games take place every day.

However, officials have since insisted that seating will not be affected.