New York City owns a creepy island that almost no one is allowed to visit - here's what it's like

Less than a mile from Manhattan - one of the priciest and most densely populated places in the world - sits a mysterious island that people abandoned more than half a century ago.

"North Brother Island is among New York City's most extraordinary and least known heritage and natural places," wrote the authors of a recent University of Pennsylvania study about the location.

The city owns the 22-acre plot, which pokes out of the East River between the South Bronx's industrial coast and a notorious prison: Rikers Island Correctional Center.

It's illegal for the public to set foot on North Brother Island and its smaller companion, South Brother Island. But even birds seem to avoid its crumbling, abandoned structures (and contrary to Broad City's depiction of the island, there isn't a package pick-up center).

In 2017, a Science Channel producers obtained the city's permission to visit North Brother Island - and the crew invited Business Insider to tag along.

The story of our small expedition premiered this month on "What on Earth?", a popular satellite-image-based TV show that's now in its fourth season. (Our segment closes out episode 12.)

Here's what we saw and learned while romping around one of New York's spookiest and most forgotten places.