High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

A charming flea market shop dedicated to retrofuturistic apparati.

The tomb of history's greatest potato promoter is surrounded by tubers.

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

An Industrial Revolution-era public work that purified water using nothing but sand.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

A wondrous old library overlooking the nation's capital.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

This exuberantly curated landscape is one of the largest sculpture gardens in Canada.

A swaggering, monumental souvenir of the most extravagant party Montreal’s ever thrown.

The vaulted ceiling is home to a scurry of “squirrelgoyles.”

Futuristic apartment blocks are the backdrop for Montreal surfers hangin' ten on the Habitat '67 standing wave.

One of Canada's oldest museums, the beautiful Redpath has been serving up Natural History and Ethnography since 1882.

This 1967 experiment in modular architecture was designed to be a new model for urban living.

These figures float and flutter in this fountain crafted by famed Swedish sculptor Carl Milles.

Conveniently located within binocular range of a nuclear bunker, the "summer camp" area was a painfully obvious spy house.

These massive concrete balls were used to mine gold in Virginia.

Please don’t anchor your boat onto the Department of Defense’s underwater data cables.