In his trusty Rockport shoes and with his dog, Heidi, by his side, lifelong New Yorker William B. Helmreich trekked 816 miles throughout Kings County in a bid to discover the “Brooklyn Nobody Knows.”

The 71-year-old’s urban walking guide, which covers 44 Brooklyn neighborhoods, takes a deep dive into the borough and is something of a follow-up to his first guide, “The New York Nobody Knows,” published in 2013.

The book includes maps like you’d find in any tourist guide, but zeroes in on hidden gems within areas off the beaten tourist track.

Helmreich, who is also a sociology professor at City College of New York, spoke to hundreds of locals to develop his guide, which illustrates how gentrification and immigration have shaped the diverse communities throughout the borough.

What do these neighborhoods have in common? Change, Helmreich says.

The author shared some of his favorite Brooklyn landmarks with amNewYork:

Newtown Creek Nature Walk in Greenpoint

Designed by sculptor George Trakas, this quarter-mile walk on Newtown Creek incorporates nature and industry. The walk “consists of trees and bushes devoted entirely to things that are used in the making of industrial products; whether it be boat ribs, fences, furniture, medicines used in pharmaceuticals and things like that,” Helmreich says.

Oriental Beach in Manhattan Beach

This beach is located at Kingsborough Community College and a visit “costs next to nothing — even has a restaurant next to it,” Helmreich says. Public visitors who apply for a permit, as well as students and faculty, can access the beach.

‘The World’s Most Famous Tree’ in Bergen Beach

Retiree Eugene Fellner has transformed the cherry tree in front of his home at 1430 E. 70th St. into a stuffed animal menagerie with some 1,140 toys. Fellner began the project in 2007 with a stuffed tiger and now the collection includes everything from Dora the Explorer to Popeye.

“The Brooklyn Nobody Knows: An Urban Walking Guide” is on sale in bookstores now for $24.95.