In the first episode of a four-part series, "Mud" traces the roots of the residential highrise, from the biblical Tower of Babel to New York's tenement buildings.

In the second episode of a four-part series, "Concrete" explores how, in New York City and globally, residential high-rises and public housing attempted to foster social equality in the 20th century.

In the third episode of a four-part series, "Glass" examines the recent proliferation of luxury condos and the growing segregation between the rich and poor.

In the final episode of a four-part series, "Home" comprises images submitted by New York Times readers, who show their lives in high-rises around the world.