Twenty-three trees, each paired with a basalt stone, line a street in Chelsea, continuing an urban project started by German Fluxus artist Joseph Beuys.

Manhattan's deadly West Side railroad, which killed hundreds of New Yorkers, is remembered by this simple plaque.

The former hotel where Tesla invented the radio.

The one-time epicenter of American songwriting is now a little remembered Manhattan commercial block.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

There are owls with glowing eyes in Herald Square.

Everyone from Mark Twain to Teddy Roosevelt has a pipe hanging from the walls of this historic chophouse.

A commemorative plaque hides a door that leads down to the New York Public Library's underground book bunker.

The former home of the reclusive "Weird Wendels" who dominated New York real estate a century before Donald Trump.

The fanciest public restroom in New York City boasts fresh flowers, art, and a classical music soundtrack.

A plaque immortalizes the spot where the early American spy said his famous last words: "I only regret that I have but one life to lose for my country."

The oldest bibliophilia club in America, with exhibitions on historic books and graphic arts.

The oldest family-run luncheonette in New York, last renovated in 1948, still serves food and drinks the old-fashioned way.

From this desk Al Hirschfeld drew his influential caricatures of the 20th century's Broadway stars.

This millstone-topped marker details the history of a mill that served as a landmark for both Union and Confederate soldiers during the American Civil War.

This marker at the entrance to the Humphreys Engineer Center honors the former Chief of the Army Corps of Engineers.

This local mascot has been a presence in the area since the 1960s.

Dedicated to a U.S. Army lieutenant colonel who was also a bird watcher and artist.

Home to a 27 room house, this estate was crafted by Black entrepreneur Olander Banks Sr.

The last vestige of a once substantial orchard and farm in the suburbs of Northern Virginia.

Built to defend Washington D.C. during the Civil War, this fort became a post-war nucleus for a thriving Black community.

The only remaining African American schoolhouse in northern Virginia is now a museum dedicated to formerly enslaved people.

Once the largest trading firm of enslaved people in the U.S., this building is now a museum that preserves Alexandria's dark past.

This little brick tunnel built by Confederate forces was used to conduct surprise attacks on the railroad.