What appears to be a bedroom is also a safe room hiding in plain sight. Credit: The New York Times

While serving as president of the New School, Bob Kerrey, the former United States senator, needed a residence befitting his station. The university moved him into a red brick Neo-Grec townhouse on West Fourth Street in Manhattan, which was previously owned by the actress Gwyneth Paltrow.

The $20,000-a-month rental had many grand spaces for entertaining, including Mr. Kerrey’s favorite, a rooftop terrace. Yet, its most unexpected amenity was quite private and secretive: a safe room.

“It looked like any old walk-in closet,” Mr. Kerrey said of the 8-feet-by-12-feet bulletproof space inside the third-floor master bedroom (a space the former Navy SEAL said he had little use for). “There was nothing about it that gave it away as anything but a place to hang your clothes.”

That is the point. For centuries, the best way for the wealthy to feel protected, or at least give the impression, […]