In recent months, city officials have set out to find answers, touring facilities across the United States and in Europe. In late September, they touched down in a place far different from New York: Norway, a welfare state with a low crime rate whose population is fairly homogeneous and smaller than New York’s.

New York and Norway also have other significant differences that raise questions about how the country’s practices can be applied in a large urban setting. The city’s new jails will be in the middle of densely populated neighborhoods, while most facilities in Norway are in rural settings. In 2018, Norway had 26 homicides — about how many New York City averages every month.

Most notably, Norway has a broad social safety net, including generous education benefits and pensions, which helps prisoners both while in prison and after their release. Inmates receive a daily allowance of about $7.60, which they can save or spend at the commissary.

Still, its incarceration system has become a model worldwide.

One stop was Halden Prison, tucked among birch and pine trees about an hour’s drive south of Oslo. It has about 200 inmates, roughly half of whom were convicted of violent crimes, including murder, rape and assault.

Inside the perimeter of 25-foot-tall smooth concrete barriers, inmates can wear their own clothing and have some freedom to move around the grounds alone. It is eerily quiet — no sounds of slamming metal doors or dangling key chains or shouting inmates and officers.

It is often considered the world’s most humane maximum-security prison.

“Halden is in this extraordinarily beautiful, rural setting, and that’s obviously not New York City,” said Ms. Glazer, who toured the property with one of the prison’s architects. “But there are elements of what’s in Halden that you can find anywhere: the openness of light, the effect of air coming through.”