Even a seasoned New York navigator can get lost in Central Park. In the sea of green and winding paths, the familiar urban grid of Manhattan disappears—often leaving both regular city slickers and tourists thoroughly disoriented. The city’s had your back all along, as it turns out. You might just not have known where to look.

Curbed reports, Central Park’s 1600 cast iron lamp posts have a hidden wayfinding trick, which was recently highlighted on a Discovery Family Channel show called Secrets of America’s Favorite Places: Central Park.

Every lamp post has four numbers at its base, like the ones below.

19th-century geolocation — four numbers on lampposts in New York’s Central Park identify its precise location. https://t.co/7t50sfnzFM — Works That Work (@WorksThatWork) April 8, 2016

Those four numbers aren't just some random designation: the first two tell you the nearest street (so above, that would be 82nd) and the second set tells you whether you’re closer to the east or west side of the park (even numbers signal east, odd signal west).

A good trick to keep in mind for anyone navigating the Big Apple with a dying battery.