Following Sunday's close of the London Olympics, the iconic Olympic flag was re-furled, repacked, and flown to its next stop — Rio de Janeiro which will host the games in 2016. The Brazilian city, the first South American city to do so, is already deep into preparations for what Rio Mayor Eduardo Paes has called an "important moment" for Brazil, but critics are warning that staging the games in the seaside metropolis will be a costly disaster. Can Rio equal London's achievement? Here, a brief guide:

How are Rio's preparations going so far?
The city will have to complete 230 construction projects, from improvements at Rio's massive port to new sports venues. While more than 65 of the jobs are already close to completion, it's too early to say whether the new athletic facilities will be ready — those aren't scheduled for delivery until 2015, with test events planned for early 2016. But critics warn that the bill is likely to dwarf the initial estimate of $14.4 billion. Trouble, they say, is already in the air.

What kind of trouble?
Some of the big construction projects have been plagued by delays and cost overruns, especially when it comes to transportation improvements. Rio's airports and roads are notoriously overcrowded, and a high-speed rail line linking Rio and Sao Paulo, Brazil's biggest city, is so far behind that officials already warn it won't be ready in time for the games. "Moving around the city is nearly impossible under normal circumstances," said Christopher Gaffney, an urbanism professor at Fluminense Federal University. "I don't see how they expect to add users."

Are there any other concerns?
Yes, plenty of them. Hotel rooms are so scarce that even after 10,000 new ones are built, city officials say they'll have to accommodate 12,000 people on cruise liners — that's what made upgrades at Rio's port necessary. Hoteliers, thanks to the country's poor schools, are having trouble hiring skilled workers to handle the expansion. Brazil's investment boom, high taxes, and labor costs are driving up the price tags on many projects before they even begin. And then there are the social costs of revamping a city of 6 million to make room for the Olympics.

What social costs?
Many of the new roads and rail lines needed to shuttle athletes and spectators to the sports venues will run through some of Rio's poorest neighborhoods. A group called the Popular Committee for the World Cup and Olympics (Rio is also hosting soccer's World Cup in 2014) has staged protests, saying that 170,000 people risk being kicked out of their homes to make way for the two events. Activists say 4,000 people living in the low-income Vila Autodromo area, where the Olympic Park is being built, will be displaced. Despite all of the concerns, though, Rio 2016 organizing committee chief executive Leonardo Gryner says the preparations are on track. "We'll get a few cold sweats," he says, "but this is normal."

Sources: Associated Press, BBC News, GlobalPost, Reuters