New York CNN  — 

The city that never sleeps is also an ever-changing one, and for its 15th anniversary, Open House New York, which finished Sunday, gave us a glimpse into architectural gems that have been repurposed and transformed over the years.

Many of the 200 participating buildings are typically closed to the public, like the Jefferson Market Library tower. Once a courthouse, fire tower and a women’s detention center, the 1877 Venetian Gothic building in Manhattan’s Greenwich Village was repurposed into a branch of the New York Public Library 50 years ago. (The brick-arched basement, where prisoners were held in cells before trial, served as the library’s Reference Room.)

Jefferson Market Library

About a mile west, on the Hudson River, is the former home of the Bell Laboratories, where innovations such as the talking movie and color television were tested. Converted into Westbeth Artists Housing in 1970, it now accommodates some 800 painters, sculptors, musicians, dancers and filmmakers in a hybrid work-live space.

“We were supposed to be one of many examples of adaptive reuse for artist residencies, but remained the first and only,” says George Cominskie, president of the tenants’ council.

Westbeth Artists Housing

Remnants of the building’s industrial history are still visible in the curvy, undulating ceilings, which could hold the weight of heavy machinery, and a train passageway.

Gwynne Duncan, a second-generation artist in the complex, has seen the neighborhood change significantly.

“It’s very crowded and touristy, but there’s a lot of benefits,” she said. “When I was a kid, by the river there would be piers on fire and it was quite dangerous. In some ways it’s better, in some ways I miss the old days.”

In Brooklyn, artists opened up shop in a very different facility: the Brooklyn Army Terminal. Built in 1918 by the US Army, this enormous concrete structure was a major military supply base. During World War II, more than 20,000 personnel were employed there. In 1981, it was transformed by the city into an industrial campus, including dozens of artist studios.

The Brooklyn Army Terminal

“The city is very focused on creating and reimagining how things are made and how to support people that make the goods and services that make New York unique,” said Esther Robinson, executive director of the arts nonprofit ArtBuilt, which is adding 40 more artist workspaces in the industrial site.

Also in Brooklyn, a 15,000-square-foot steel fabrication plant was converted into a brewery, where Five Boroughs Brewing Co. produces all of its beer. Railroad tracks, gantry cranes and prewar hexagonal steel rebar can still be seen in the facility.

Some locations were shown as part of Open House New York for the first time, like the French Embassy on Fifth Avenue, one of the few remaining examples of Gilded Age architecture; and the American Copper buildings, an 800-unit luxury rental community with a bridge-pool hybrid connecting its two towers, allowing people to literally swim from one building to the next.