6 / 20

PAKISTAN-UNREST-KARACHI

People gather on the site of bomb blast in Karachi on March 3, 2013. A bomb attack in Pakistan's largest city Karachi on Sunday killed at least 23 people, including women and children, and wounded 50 others, police said. AFP PHOTO/ASIF HASSAN (Photo credit should read ASIF HASSAN/AFP/Getty Images)

World's best and worst cities to live in

Melbourne holds the top spot as the most livable city for the third year

in a row, according a report by the Economist Intelligence Unit. The

study, based on 30 factors such as quality of health care and threat of

military conflict, ranked 140 cities.