One of Philadelphia's largest murals resides hidden under this bridge.

In the bowels of a 19th-century brewery lurks a fine-dining restaurant offering an array of themed feasts.

The oldest family-run restaurant in the United States is a living museum of New Orleans dining history.

The notorious headquarters of a corrupt political machine.

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

This monument to a veteran of the Mexican-American War is one of only two in Manhattan that serve as an actual mausoleum.

Two large-scale sculptures of Adam and Eve greet visitors in the nude at the Time Warner Center in NYC.

This Orthodox Church's exterior is rather unorthodox.

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

A replica of a 7th-century church hides in plain sight in the middle of the concrete jungle.

One of the first major shipyards in Brooklyn.

On the top floor of an upscale department store stands a lavish restaurant housed in a replica of a luxury French dining car.

What happens here stays here – unless it affects the whole world.

Once a flowing stream and where the USS Monitor, the world's first ironclad, was built and launched.

Come for the waffles, stay for more waffles.

Where the Monitor was launched and ushered in the age of the "ironclads."

Storage warehouse of the rich and famous.

Ornate "Renaissance Revival" style building.

The only remaining Jewish congregation in Greenpoint.

HBO series' stage tucked away in a Greenpoint lot is the largest theatrical set of its kind in the United States.

Built as a home for the Union Porcelain magnate in 1867, now the Greenpoint Reformed Church and home to a ceramic mystery.

Neoclassical bank designed by NY architects Helmle & Huberty.

Enormous one time fiber mill now houses local artists and small businesses.

This Upper East Side apartment co-op was designed as a tuberculosis sanitarium.