The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Graffiti from the 16th and 17th centuries cover the walls of this part of the Tower of London.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

An exercise in radical design and social living that became the epicenter of Soviet spy networks in London.

Its collection includes a broad array of social, geographic, graphic design, and political history.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

The famous winding walk at Chartres is surrounded in mystery and myth.

Measuring approximately 200 feet long, Swampy is the world's largest alligator-shaped building.

Massive prehistoric mammals used these stones as oversized scratching posts.

The southernmost outpost of the Russian Empire in colonial America.

Louisa May Alcott based “Little Women” on her experiences growing up in this house with her sisters.

One of the oldest carousels in the United States is still running in the coastal village of Watch Hill.

The last remaining attraction from Paragon Park.

Plans for this peninsula included houses, the United Nations Headquarters, and a nuclear power plant. When none of them worked out, it became an expansive park.

These beautiful garden buildings are among the oldest surviving greenhouses in the United States.

No one really knows how these old hobby horses got here, but the herd keeps growing.

A building so large that it has its own weather.

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

It may look like no more than a full-scale model, but every part of this full Space Shuttle stack had a working role in aviation history.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.