This mysterious marker puzzles pedestrians and infuriates geographers.

Where the four original members of the Ramones hung out and revolutionized punk rock.

The oldest living organism in New York City. Maybe.

A remnant from the golden age of aviation still in use today, Pan Am's Clipper service took off from this Art Deco gem.

The preserved house of a jazz legend still echoes with his music.

A uniquely lettered street sign marks the corner where the iconic word game was invented.

Holding the most bodies of any cemetery in the United States.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

Abandoned 19th century homes once occupied by naval officers, soon to be demolished.

A century-old magnolia tree is the only living landmark tree in New York City.

The unassuming structure was part of a Major League Baseball stadium.

A one-ton statue of Steve Rogers beautifies the entry to a Brooklyn Bed, Bath & Beyond.

One of Frank Lloyd Wright's final works was this UFO church.

An off-the-beaten-path place to literally hang beneath Milwaukee's Holton Street Bridge.

Hot Doug's "Hot Dog" Stand.

An unassuming store hides relics of its former life as the jazz club that hosted some of the best black performers of the 1920s and '30s.

In Chicago, a pizza-enthusiast has opened a museum dedicated to the history of pizza.

A century-old network of freight tunnels underneath the city's historic business district.

Hidden on the 7th floor of a historic building, this Cajun spot features wall-to-wall bottles of hot sauce.

The last masonry skyscraper ever built reveals a transitional moment in architectural history.

Chicago's Navy Pier on Lake Michigan was a training hub for aircraft carrier pilots during WWII.

Partially submerged Buddha heads freckle Chicago’s neighborhoods.

A 400-foot-tall tall map of Chicago makes this once-ignored building stand out.

This memorial plaque remembers a strangely shallow maritime disaster known as "Chicago's Titanic."