This nearly invisible wire transforms much of the city into one big, symbolic home on the holy day.

This banal Parisian entranceway is not what it seems.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

This museum in a Paris apartment gives a unique look at the iconic French singer's life.

Peeing dogs guard the Roman hunting goddess atop a fountain at France’s Château de Fontainebleau.

This Manhattan skyscraper is a reminder of the brief but glorious age of urban air taxis.

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

A hidden "place of interment for gentlemen."

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

This historic building housed the surviving crew members of the Titanic, who were left destitute after the wreck.

New York City's first Modernist house.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

These ornate manhole covers were used for a now-forgotten purpose.

Life-size bronzes of the Grinch, Cat in the Hat, Yertle the Turtle, Sam-I-Am, and the Lorax—and the author himself.

This block in downtown Brooklyn was a hotbed of antislavery activism along the Underground Railroad.

In this Parisian garden's grotesque former life as a zoo it fed exotic animals to the bourgeois and put humans on exhibit.

The home of the first American-born saint is one of the only curved buildings in New York.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

Striking occult iconography on a medieval German church.

Go take a picture with the inventor of the daguerreotype photographic process.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

This wall on a street corner in Lower Manhattan has been a blank canvas for a rotation of renowned artists since the 1980s.

Rat sculptures try to infiltrate the Graybar Building in an architectural tribute to New York City's nautical history.