With approximately 40 million annual visitors, Central Park stands as the most visited urban park in the United States. Navigating its long, winding paths across 843 acres can expectedly get quite tricky—even for the most seasoned New Yorkers. If you ever find yourself lost in a sea of green, there’s a way to reorient yourself without having to rely on dubious data networks or Google Maps: just head to one of Central Park’s 1,600 lamp posts, which serve as unlikely navigational devices.

We’ll be sharing many secrets like this on our next walking tour of Central Park, which takes place this weekend. Until then, here’s a spotlight on one of our favorite “Untapped” secrets:

Secrets of Central Park Walking Tour

Also known as “luminaires,” Central Park’s decorative lamp posts feature plaques with four numbers embossed onto them. The first two indicate the closest cross street, and the last two numbers indicate which side of the park the lamp is closer to: even numbers, in this case, mean the east side, and odd numbers mean west. The last two digits also indicate location, with the numbers increasing as you move closer to the center of the park.

Newer lamppost navigational devices in Central Park

A lamp post with the number “6202,” for instance, translates to a location on the east side aligned with 62nd Street.

“The last two digits increase as one moves toward the center of the park,” explained writer Susan Merrit in Works That Work. This numerical system was originally designed to help park employees locate lamps in need of service or repair, but it’s has since become a useful tool for in-the-know park visitors.

For more secrets of Central Park, join us on our next walking tour:

Secrets of Central Park Walking Tour
Next, check out The Top 10 Secrets of the Central Park Zoo and The Secrets of Central Park’s Winter Routine.

Check out all of our Behind the Scenes Tours.