Perhaps the most scandalous statue of America's first president.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

Largest Roman Catholic church in North America.

A Spiritualist house of worship where believers communicate with the dead in the spirit world.

The walls of the iconic dome are hollow and have a secret stairway.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

People escaping slavery may have hidden inside a corpse vault.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

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

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

A painfully obvious spy house sits right across the street from the Russian Embassy.

Home to items never before seen by the public.

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

The walls of this small village have been turned into a living street art gallery.

An abandoned mine now resembles a post-apocalyptic landscape of derelict buildings and blood-red pools of water.

Hidden beneath a beautiful overlook you’ll find the history of the city depicted in comic strip format next to a pay toilet.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

An exquisite collection of fairytale conveyances that puts most car museums to shame.

Entire apothecaries are on display at this Lisbon museum, which explores the history of medicine.

This unique architectural wonder is also tied to one of the 20th-century's most renowned writers.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

An abandoned tuberculosis hospital said to be haunted by the patients who died within its walls.

This historic streetcar system has been running since the 19th-century.