Beijing, China
Kay, 23, lives in Gulou, a neighborhood that still feels like "Old Beijing." Many buildings like hers were demolished ahead of the 2008 Olympics to make way for luxury accommodations.
Abu Dhabi, U.A.E.
Aisha Mohammed, 25, lives outside the ultramodern city's limits in a desert village, where temperatures can reach 130 degrees.
Buenos Aires, Argentina
Carla Sgarbi and Mariana Bayle, both 26, have been friends since they were 1-year-olds, so they're comfortable sharing a very small space in the center of the city.
Athens, Greece
Eugenie Manisalidi, 25, lives in a big apartment in the southern part of Athens. She lives alone, but her mother and grandmother live in the same building. Manisalidi fell in love with hip-hop and African culture at age 17 and has amassed a collection of posters and books that color her walls. She has traveled to Africa and wants to move to Ghana.
Cairo, Egypt
Enas Sherif, 22, was born in a small village in the desert three hours south of Cairo, but now she lives with her family in the eastern part of the city. Sherif, who wants to be a flight attendant for an Egyptian airline one day, says the poster on the wall behind her bed makes her "dream of traveling to places far from Egypt."
Tokyo, Japan
Mayu Shimura, 22, lives with her parents and younger sister in a big house in the northern part of Tokyo. She loves the color green and decorated her room—and even her Italian greyhound named Mer—in the hue.