A fire burned Sunday at the National Museum in Rio de Janeiro. Buda Mendes/Getty Images hide caption

Kurdish mathematician Caucher Birkar (right) received the Fields Medal, math's most prestigious prize, during the International Congress of Mathematicians in Rio de Janeiro on Wednesday. The medal was stolen soon after. AFP/Getty Images hide caption

Brazil's President Michel Temer has ordered that the military take over security issues in Rio de Janeiro. Leo Correa/AP hide caption

Revelers celebrate during the Carnival street parade of the Bloco das Carmelitas in the Santa Teresa neighborhood in Rio de Janeiro, Brazil, last week. Mauro Pimentel/AFP/Getty Images hide caption

Davi de Oliveira Moreira, known as "Sereio" (merman in Portuguese), poses in costume at Arpoador Rock on Ipanema Beach in Rio de Janeiro, Brazil, last May. Yasuyoshi Chiba/AFP/Getty Images hide caption

Soldiers pass a woman in an alley in the Rocinha favela of Rio de Janeiro on Friday, during an operation related to an apparent war among drug dealers. Leo Correa/AP hide caption

Maracanã Stadium's turf is dry, worn and filled with ruts and holes. Those soccer clubs that call the stadium home plan to meet and discuss how to bring Maracanã up to game-worthy shape. The question is, who will pay for the repairs? Nacho Doce/Reuters hide caption

Guide Wesley Williams (left) lines up blind long jumper and sprinter Lex Gillette on the track before making a long jump during practice at the U.S. Olympic Training Center in San Diego. Gillette started losing his sight when he was 8 years old. Bill Wechter for NPR hide caption

Rio's Olympic beach volleyball venue is on Copacabana beach. Marcio Jose Sanchez/AP hide caption

Lucia Cabral peers through a bullet hole in her door in the Alemao favela complex. Like people everywhere, she checks her phone soon after she wakes up in the morning. In these favelas, she says, it's a matter of life or death. Joao Velozo for NPR hide caption

Cleaners in Rio de Janeiro collect debris from Guanabara Bay that washed up onto the beach last December. The bay, which will host sailing events at the Olympics in August, is heavily polluted. Yasuyoshi Chiba/AFP/Getty Images hide caption

Jason Pryor is the only U.S. men's epee fencer competing at the Olympics in Rio. He is currently ranked 38th in the world. Adrienne Grunwald for NPR hide caption

Zulema Arenas #548 of Peru competes in the women's 3000 meter steeplechase during the Ibero American Athletics Championships - Aquece Rio Test Event for the Rio 2016 Olympics at Olympic Stadium on May 14, 2016 in Rio de Janeiro. Matthew Stockman/Getty Images hide caption

A man performs yoga in the Babilonia favela overlooking Rio de Janeiro in 2014. The Brazilian government made a big push to impose order on the shantytowns in advance of the World Cup in 2014 and the Olympics this summer. Babilonia was once considered a model, but violence has been on the rise in the run-up to the games. Mario Tama/Getty Images hide caption

Lourdes Garcia-Navarro performs with the Vila Isabel Samba School during Carnival in Rio de Janeiro. André Vieira for NPR hide caption